Resist composition and method of forming resist pattern

ABSTRACT

A resist composition including a resin component having a constitutional unit derived from a compound represented by General Formula (a01-1) and a constitutional unit derived from a compound represented by General Formula (a02-1), and an acid generator component composed of an anion moiety and a cation moiety. In General Formula (a01-1), W 1  represents a polymerizable group-containing group, C t  represents a tertiary carbon atom, R 11  represents an unsaturated hydrocarbon group which may have a substituent, R 12  and R 13  represent a chain saturated hydrocarbon group which may have a substituent, and a carbon atom at an α-position of C t  constitutes a carbon-carbon unsaturated bond. In General Formula (a02-1), W 2  represents a polymerizable group-containing group, Wa 2  represents an aromatic hydrocarbon group, and n2 represents an integer in a range of 1 to 3

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a resist composition and a method of forming a resist pattern.

Priority is claimed on Japanese Patent Application No. 2019-228281, filed on Dec. 18, 2019, the content of which is incorporated herein by reference.

Description of Related Art

In recent years, in the production of semiconductor elements and liquid crystal display elements, with advances in lithography techniques, rapid progress in the field of pattern miniaturization has been achieved. Typically, these miniaturization techniques involve shortening the wavelength (increasing the energy) of the light source for exposure.

Resist materials for use with these types of light sources for exposure require lithography characteristics such as a high resolution capable of reproducing patterns of fine dimensions, and a high level of sensitivity to these types of light sources for exposure.

As a resist material that satisfies these requirements, a chemical amplification-type resist composition which contains a base material component having solubility in a developing solution, which is changed by action of an acid, and an acid generator component generating an acid upon exposure has been conventionally used.

In the chemical amplification-type resist composition, a resin having a plurality of constitutional units is generally used in order to improve lithography characteristics and the like.

For example, Japanese Unexamined Patent Application, First Publication No. 2018-124548 discloses a resist composition or the like that employs a high-molecular-weight compound having two specific constitutional units to improve lithography characteristics.

SUMMARY OF THE INVENTION

Recently, with further advances in lithography techniques, rapid progress in the field of pattern miniaturization is being achieved together with the expansion of application fields. Along with this progress, in a case where manufacturing a semiconductor element or the like, a technique capable of forming, in a good shape, a fine pattern having a pattern width dimension of less than 100 nm is required.

However, in the conventional resist composition such as that described in Japanese Unexamined Patent Application, First Publication No. 2018-124548 described above, the achievement of both high sensitivity and lithography characteristics is difficult in a case where a fine pattern is formed at the level of dimensions described above.

The present invention has been made in consideration of the above circumstances, an object of the present invention is to provide a resist composition, with which high sensitivity can be achieved, which is excellent in lithography characteristics, and with which a resist pattern having high rectangularity can be formed, and a method of forming a resist pattern by using the resist composition.

In order to achieve the above-described object, the present invention employs the following configurations.

That is, the first aspect of the present invention is a resist composition generating an acid upon exposure and having solubility in a developing solution, which is changed by action of an acid. The resist composition contains a resin component (A1) having solubility in a developing solution, which is changed by action of an acid, and an acid generator component (B) generating an acid upon exposure. The resin component (A1) has a constitutional unit (a01) derived from a compound represented by General Formula (a01-1) and a constitutional unit (a02) derived from a compound represented by General Formula (a02-1). The acid generator component (B) is composed of a compound (B1) having an anion moiety and a cation moiety.

In General Formula (a01-1), W¹ represents a polymerizable group-containing group. C^(t) represents a tertiary carbon atom. R¹¹ represents an unsaturated hydrocarbon group which may have a substituent. R¹² and R¹³ each independently represent a chain saturated hydrocarbon group which may have a substituent. However, a carbon atom at an α-position of C^(t) constitutes a carbon-carbon unsaturated bond. In General Formula (a02-1), W² represents a polymerizable group-containing group. Wa² represents an aromatic hydrocarbon group. Part or all of hydrogen atoms which the aromatic hydrocarbon group has may be substituted with a substituent other than a hydroxy group. W² and Wa² may form a condensed ring. n2 represents an integer in a range of 1 to 3.

The second aspect of the present invention is a method of forming a resist pattern, including a step of forming a resist film on a support using the resist composition according to the first aspect, a step of exposing the resist film, and a step of developing the exposed resist film to form a resist pattern.

According to the present invention, it is possible to provide a resist composition, with which high sensitivity can be achieved, which is excellent in lithography characteristics, and with which a resist pattern having high rectangularity can be formed, and a method of forming a resist pattern by using the resist composition.

DETAILED DESCRIPTION OF THE INVENTION

In the present specification and the scope of the present patent claims, the term “aliphatic” is a relative concept used with respect to the term “aromatic” and defines a group or compound that has no aromaticity.

The term “alkyl group” includes a monovalent saturated hydrocarbon group that is linear, branched, or cyclic, unless otherwise specified. The same applies to the alkyl group of an alkoxy group.

The term “alkylene group” includes a divalent saturated hydrocarbon group that is linear, branched, or cyclic, unless otherwise specified.

Examples of the “halogen atom” include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The term “constitutional unit” means a monomer unit (monomeric unit) that contributes to the formation of a high-molecular-weight compound (a resin, a polymer, or a copolymer).

In a case where “may have a substituent” is described, both of a case where a hydrogen atom (—H) is substituted with a monovalent group and a case where a methylene group (—CH₂—) is substituted with a divalent group are included.

The term “exposure” is used as a general concept that includes irradiation with any form of radiation.

The term “acid-decomposable group” indicates a group in which at least a part of a bond in the structure of the acid-decomposable group can be cleaved by action of an acid.

Examples of the acid-decomposable group having a polarity which is increased by action of an acid include groups which are decomposed by action of an acid to generate a polar group.

Examples of the polar group include a carboxy group, a hydroxy group, an amino group, and a sulfo group (—SO₃H)

More specific examples of the acid-decomposable group include a group in which the above-described polar group has been protected with an acid-dissociable group (such as a group in which a hydrogen atom of the OH-containing polar group has been protected with an acid-dissociable group).

The “acid-dissociable group” indicates any one of (i) a group having acid dissociability, in which a bond between the acid-dissociable group and an atom adjacent to the acid-dissociable group can be cleaved by action of an acid; and (ii) a group in which a part of bonds are cleaved by action of an acid, and then a decarboxylation reaction occurs, thereby cleaving the bond between the acid-dissociable group and the atom adjacent to the acid-dissociable group.

It is necessary that the acid-dissociable group that constitutes the acid-decomposable group be a group that exhibits a lower polarity than the polar group generated by the dissociation of the acid-dissociable group. Thus, in a case where the acid-dissociable group is dissociated by action of an acid, a polar group exhibiting a higher polarity than the acid-dissociable group is generated, thereby increasing the polarity. As a result, the polarity of the entire component (A1) is increased. By the increase in the polarity, the solubility in a developing solution relatively changes. The solubility in a developing solution is increased in a case where the developing solution is an alkali developing solution, whereas the solubility in a developing solution is decreased in a case where the developing solution is an organic developing solution.

The “base material component” is an organic compound having a film-forming ability. The organic compounds used as the base material component are roughly classified into a non-polymer and a polymer. As the non-polymer, those having a molecular weight of 500 or more and less than 4,000 are usually used. Hereinafter, a “low-molecular-weight compound” refers to a non-polymer having a molecular weight of 500 or more and less than 4,000. As the polymer, those having a molecular weight of 1,000 or more are usually used. Hereinafter, a “resin”, a “high-molecular-weight compound”, or a “polymer” refers to a polymer having a molecular weight of 1,000 or more. As the molecular weight of the polymer, a polystyrene-equivalent mass-average molecular weight determined by gel permeation chromatography (GPC) is used.

A “constitutional unit derived from” means a constitutional unit that is formed by the cleavage of a multiple bond between carbon atoms, for example, an ethylenic double bond.

In the “acrylic acid ester”, the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent. The substituent (R^(αx)) that is substituted for the hydrogen atom bonded to the carbon atom at the α-position is an atom other than a hydrogen atom or a group. Further, itaconic acid diester in which the substituent (R^(αx)) is substituted with a substituent having an ester bond or α-hydroxyacryl ester in which the substituent (Ra) is substituted with a hydroxyalkyl group or with a group in which a hydroxy group is modified can be included as an acrylic acid ester. A carbon atom at the α-position of acrylic acid ester indicates the carbon atom bonded to the carbonyl group of acrylic acid, unless otherwise specified.

Hereinafter, acrylic acid ester in which the hydrogen atom bonded to the carbon atom at the α-position is substituted with a substituent is also referred to as an α-substituted acrylic acid ester.

The term “derivative” includes a compound in which the hydrogen atom at the α-position of the object compound has been substituted with another substituent such as an alkyl group or a halogenated alkyl group; and derivatives thereof. Examples of the derivatives thereof include a derivative in which the hydrogen atom of the hydroxy group of the object compound in which the hydrogen atom at the α-position may be substituted with a substituent is substituted with an organic group; and a derivative in which a substituent other than a hydroxy group is bonded to the object compound in which the hydrogen atom at the α-position may be substituted with a substituent. The α-position refers to the first carbon atom adjacent to the functional group unless otherwise specified.

Examples of the substituent that is substituted for the hydrogen atom at the α-position of hydroxystyrene include the same group as R^(αx).

In the present specification and the scope of the present patent claims, asymmetric carbon atoms may be present, and thus enantiomers or diastereomers may be present depending on the structures of the chemical formula. In that case, these isomers are represented by one chemical formula. These isomers may be used alone or in the form of a mixture.

(Resist Composition)

The resist composition according to the present embodiment is a resist composition that generates an acid upon exposure and having solubility in a developing solution, which is changed by action of an acid. Such a resist composition contains a base material component (A) (hereinafter, also referred to as a “component (A)”) having solubility in a developing solution, which is changed by action of an acid, and an acid generator component (B) (hereinafter, also referred to as a “component (B)”) generating an acid upon exposure.

In a case where a resist film is formed using the resist composition according to the present embodiment and then the formed resist film is subjected to selective exposure, an acid is generated from the component (B) at the exposed portion of the resist film, and the generated acid acts on the component (A) to change the solubility of the component (A) in a developing solution, whereas the solubility of the component (A) in a developing solution is not changed at the unexposed portion of the resist film, whereby the difference in solubility in the developing solution between the exposed portion and the unexposed portion of the resist film is generated. Therefore, by subjecting the resist film to development, the exposed portion of the resist film is dissolved and removed to form a positive-tone resist pattern in a case where the resist composition is a positive-tone type composition, whereas the unexposed portion of the resist film is dissolved and removed to form a negative-tone resist pattern in a case where the resist composition is a negative-tone type composition.

In the present specification, a resist composition which forms a positive-tone resist pattern by dissolving and removing the exposed portion of the resist film is called a positive-tone resist composition, and a resist composition which forms a negative-tone resist pattern by dissolving and removing the unexposed portion of the resist film is called a negative-tone resist composition. The resist composition according to the present embodiment may be a positive-tone resist composition or a negative-tone resist composition.

Further, in the formation of a resist pattern, the resist composition according to the present embodiment can be applied to an alkali developing process using an alkali developing solution in the developing treatment, or a solvent developing process using a developing solution containing an organic solvent (organic developing solution) in the developing treatment.

<Component (A)>

In the resist composition according to the present embodiment, the component (A) contains a resin component (A1) (hereinafter, also referred to as a “component (A1)”) having solubility in a developing solution, which is changed by action of an acid. In the alkali developing process and the solvent developing process, since the polarity of the base material component before and after the exposure is changed by using the component (A1), an excellent development contrast can be obtained.

As the component (A), at least the component (A1) is used, and another resin component and/or a low-molecular-weight compound may be used in combination with the component (A1).

In a case of applying an alkali developing process, a base material component containing the component (A1) is substantially insoluble in an alkali developing solution prior to exposure, but in a case where an acid is generated from the component (B) upon exposure, the action of this acid causes an increase in the polarity of the base material component, thereby increasing the solubility of the base material component in an alkali developing solution. Therefore, in the formation of a resist pattern, by performing selective exposure of a resist film formed by applying the resist composition onto a support, the exposed portion of the resist film changes from an insoluble state to a soluble state in an alkali developing solution, whereas the unexposed portion of the resist film remains insoluble in an alkali developing solution, and thus, a positive-tone resist pattern is formed by alkali developing.

On the other hand, in a case of a solvent developing process, the base material component containing the component (A1) exhibits high solubility in an organic developing solution prior to exposure, and in a case where an acid is generated from the component (B) upon exposure, the polarity of the component (A1) is increased by the action of the generated acid, thereby decreasing the solubility of the component (A1) in an organic developing solution. Therefore, in the formation of a resist pattern, by performing selective exposure of a resist film formed by applying the resist composition onto a support, the exposed portion of the resist film changes from a soluble state to an insoluble state in an organic developing solution, whereas the unexposed portion of the resist film remains soluble and does not change, thereby a contrast between the exposed portion and the unexposed portion can be obtained, and thus a negative-tone resist pattern is formed by developing in the organic developing solution.

In the resist composition according to the present embodiment, the component (A) may be used alone or in a combination of two or more kinds thereof.

In Regard to Component (A1)

The component (A1) is a resin component having solubility in a developing solution, which is changed by action of an acid. The component (A1) has a constitutional unit (a01) derived from a compound represented by General Formula (a01-1) and a constitutional unit (a02) derived from a compound represented by General Formula (a02-1), which are described later.

The component (A1) may have other constitutional units as necessary in addition to the constitutional unit (a01) and the constitutional unit (a02).

<<Constitutional Unit (a01)>>

The constitutional unit (a01) is a constitutional unit derived from a compound represented by General Formula (a01-1).

In the constitutional unit (a01), the side chain terminal group “—C^(t)(R¹¹)(R¹²)(R¹³)” in General Formula (a01-1) is an acid-dissociable group, and this acid-dissociable group protects the oxy group (—O—) side of the carbonyloxy group [—C(═O)—O—] in General Formula (a01-1).

Here, the “acid-dissociable group” has acid dissociability, which means a bond between the acid-dissociable group and an oxygen atom (an oxy group (—O—)) adjacent to the acid-dissociable group can be cleaved by action of an acid. In a case where the acid-dissociable group is dissociated by action of an acid, a polar group having a higher polarity than the acid-dissociable group is generated, and thus the polarity is increased. As a result, the polarity of the entire component (A1) is increased. By the increase in the polarity, the solubility in a developing solution relatively changes. The solubility in a developing solution is increased in a case where the developing solution is an alkali developing solution, whereas the solubility in a developing solution is decreased in a case where the developing solution is an organic developing solution.

In General Formula (a01-1), W¹ represents a polymerizable group-containing group. C^(t) represents a tertiary carbon atom. R¹¹ represents an unsaturated hydrocarbon group which may have a substituent. R¹² and R¹³ each independently represent a chain saturated hydrocarbon group which may have a substituent. However, a carbon atom at an α-position of C^(t) constitutes a carbon-carbon unsaturated bond.

In General Formula (a01-1), W¹ represents a polymerizable group-containing group.

The “polymerizable group” as W¹ is a group that enables a compound having the polymerizable group to be polymerized by radical polymerization or the like, and includes a group containing a multiple bond between carbon atoms, such as an ethylenic double bond.

Examples of the polymerizable group as W¹ include a vinyl group, an allyl group, acryloyl group, a methacryloyl group, a fluorovinyl group, a difluorovinyl group, a trifluorovinyl group, a difluorotrifluoromethylvinyl group, a trifluoroallyl group, a perfluoroallyl group, a trifluoromethylacryloyl group, a nonylfluorobutylacryloyl group, a vinyl ether group, a fluorine-containing vinyl ether group, an allyl ether group, a fluorine-containing allyl ether group, a styryl group, and a vinylnaphthyl group, a fluorine-containing styryl group, a fluorine-containing vinylnaphthyl group, a norbornyl group, a fluorine-containing norbornyl group, and a silyl group.

The “polymerizable group-containing group” as W¹ may be a group composed of only a polymerizable group, or a group composed of a polymerizable group and a group other than the polymerizable group. Examples of the group other than the polymerizable group include a divalent hydrocarbon group which may have a substituent and a divalent linking group containing a hetero atom.

Divalent Hydrocarbon Group which May have Substituent:

In a case where the group other than the polymerizable group represents a divalent hydrocarbon group which may have a substituent, the hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group.

Aliphatic Hydrocarbon Group as Group Other than the Polymerizable Group

The aliphatic hydrocarbon group indicates a hydrocarbon group that has no aromaticity. The aliphatic hydrocarbon group may be saturated or unsaturated. In general, it is preferable that the aliphatic hydrocarbon group be saturated. Examples of the aliphatic hydrocarbon group include a linear or branched aliphatic hydrocarbon group, and an aliphatic hydrocarbon group containing a ring in the structure thereof.

Linear or Branched Aliphatic Hydrocarbon Group

The linear aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbon atoms.

The linear aliphatic hydrocarbon group is preferably a linear alkylene group, and specific examples thereof include a methylene group [—CH₂—], an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], a tetramethylene group [—(CH₂)₄—], and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group preferably has 2 to 10 carbon atoms, more preferably 3 to 6 carbon atoms, still more preferably 3 or 4 carbon atoms, and most preferably 3 carbon atoms.

The branched aliphatic hydrocarbon group is preferably a branched alkylene group, and specific examples thereof include alkylalkylene groups, for example, alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—; alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; and alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and —CH₂CH(CH₃)CH₂CH₂—. The alkyl group in the alkylalkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

The linear or branched aliphatic hydrocarbon group may or may not have a substituent. Examples of the substituent include a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms, which has been substituted with a fluorine atom, and a carbonyl group.

Aliphatic Hydrocarbon Group Containing Ring in Structure Thereof

Examples of the aliphatic hydrocarbon group containing a ring in the structure thereof include a cyclic aliphatic hydrocarbon group which may have a substituent containing a hetero atom in the ring structure thereof (a group in which two hydrogen atoms have been removed from an aliphatic hydrocarbon ring), a group in which the cyclic aliphatic hydrocarbon group is bonded to the terminal of a linear or branched aliphatic hydrocarbon group, and a group in which the cyclic aliphatic hydrocarbon group is interposed in a linear or branched aliphatic hydrocarbon group. Examples of the linear or branched aliphatic hydrocarbon group include the same groups as those described above.

The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbon atoms and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be a polycyclic group or a monocyclic group. The monocyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a polycycloalkane, and the polycycloalkane is preferably a group having 7 to 12 carbon atoms. Specific examples of the polycyclic alicyclic hydrocarbon group include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxy group, and a carbonyl group.

The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and most preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group.

The alkoxy group as the substituent is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, or a tert-butoxy group, and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom for the substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is preferable.

Examples of the halogenated alkyl group as the substituent include groups in which part or all of hydrogen atoms in the above-described alkyl groups have been substituted with the above-described halogen atom.

In the cyclic aliphatic hydrocarbon group, a part of carbon atoms constituting the ring structure thereof may be substituted with a substituent containing a hetero atom. The substituent containing a hetero atom is preferably —O—, —C(═O)—O—, —S—, —S(═O)₂—, or —S(═O)₂—O—.

Aromatic Hydrocarbon Group as Group Other than the Polymerizable Group

The aromatic hydrocarbon group is a hydrocarbon group having at least one aromatic ring.

The aromatic ring is not particularly limited as long as it is a cyclic conjugated system having (4n+2) π electrons, and may be monocyclic or polycyclic. The aromatic ring preferably has 5 to 30 carbon atoms, more preferably 5 to 20 carbon atoms, still more preferably 6 to 15 carbon atoms, and particularly preferably 6 to 12 carbon atoms. Here, the number of carbon atoms in a substituent is not included in the number of carbon atoms. Specific examples of the aromatic ring include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; and an aromatic heterocyclic ring in which a part of carbon atoms constituting the above-described aromatic hydrocarbon ring have been substituted with a hetero atom. Examples of the hetero atom in the aromatic heterocyclic rings include an oxygen atom, a sulfur atom, and a nitrogen atom. Specific examples of the aromatic heterocyclic ring include a pyridine ring and a thiophene ring.

Specific examples of the aromatic hydrocarbon group include a group in which two hydrogen atoms have been removed from the above-described aromatic hydrocarbon ring or aromatic heterocyclic ring (an arylene group or a heteroarylene group); a group in which two hydrogen atoms have been removed from an aromatic compound having two or more aromatic rings (such as biphenyl or fluorene); and a group in which one hydrogen atom of a group (an aryl group or a heteroaryl group) obtained by removing one hydrogen atom from the above-described aromatic hydrocarbon ring or aromatic heterocyclic ring has been substituted with an alkylene group (for example, a group in which one hydrogen atom has been further removed from an aryl group in arylalkyl groups such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethyl group). The alkylene group bonded to the aryl group or the heteroaryl group preferably has 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms, and particularly preferably 1 carbon atom.

In the aromatic hydrocarbon group, the hydrogen atom which the aromatic hydrocarbon group has may be substituted with a substituent. For example, the hydrogen atom bonded to the aromatic ring in the aromatic hydrocarbon group may be substituted with a substituent. Examples of substituents include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, and a hydroxy group.

The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and most preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group.

Examples of the alkoxy group, the halogen atom, and the halogenated alkyl group, as the substituent, include the same groups as those exemplified as the substituent that is substituted for a hydrogen atom which the cyclic aliphatic hydrocarbon group has.

Divalent Linking Group Containing Hetero Atom

In a case where the group other than the polymerizable group represents a divalent linking group containing a hetero atom, preferred examples of the linking group include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O— —C(═O)—NH—, —NH—, —NH—C(═NH)— (H may be substituted with a substituent such as an alkyl group, an acyl group, or the like), —S—, —S(═O)₂—, —S(═O)₂—O—, and a group represented by General Formula: —Y²—O—Y²², —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—, —[Y²¹—C(═O)—O]_(m″), —Y²¹—, —Y²¹—O—C(═O)—Y²²— or —Y²¹—S(═O)₂—O—Y²²— [in the formulae, Y²¹ and Y²² each independently represent a divalent hydrocarbon group which may have a substituent, 0 represents an oxygen atom, and m″ represents an integer in a range of 0 to 3].

In a case where the divalent linking group containing a hetero atom is —C(═O)—NH—, —C(═O)—NH—C(═O)—, —NH—, or —NH—C(═NH)—, H may be substituted with a substituent such as an alkyl group, an acyl group, or the like. The substituent (an alkyl group, an acyl group, or the like) preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 5 carbon atoms.

In General Formulae —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—, —[Y²¹—C(═O)—O]_(m″), —Y²², —Y²¹—O—C(═O)—Y²²—, and —Y²¹—S(═O)₂—O—Y²²—, Y²¹, and Y²² each independently represent a divalent hydrocarbon group which may have a substituent. Examples of the divalent hydrocarbon group include those (mentioned as the divalent hydrocarbon group which may have a substituent) in the description of the above-described divalent linking group.

Y²¹ is preferably a linear aliphatic hydrocarbon group, more preferably a linear alkylene group, still more preferably a linear alkylene group having 1 to 5 carbon atoms, and particularly preferably a methylene group or an ethylene group.

Y²² is preferably a linear or branched aliphatic hydrocarbon group and more preferably a methylene group, an ethylene group, or an alkylmethylene group. The alkyl group in the alkylmethylene group is preferably a linear alkyl group having 1 to 5 carbon atoms, more preferably a linear alkyl group having 1 to 3 carbon atoms, and most preferably a methyl group.

In the group represented by Formula —[Y²—C(═O)—O]_(m″)—Y²²—, m″ represents an integer in a range of 0 to 3, preferably an integer in a range of 0 to 2, more preferably 0 or 1, and particularly preferably 1. In other words, it is particularly preferable that the group represented by Formula —[Y²¹—C(═O)—O]_(m″)—Y²²— represent a group represented by Formula —Y²¹—C(═O)—O—Y²²—. Among them, a group represented by Formula —(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)— is preferable. In the formula, a′ represents an integer in a range of 1 to 10, preferably an integer in a range of 1 to 8, more preferably an integer in a range of 1 to 5, still more preferably 1 or 2, and most preferably 1. b′ represents an integer in a range of 1 to 10, preferably an integer in a range of 1 to 8, more preferably an integer in a range of 1 to 5, still more preferably 1 or 2, and most preferably 1.

Among the above, the group other than the polymerizable group is preferably an ester bond [—C(═O)—O— or —O—C(═O)—], an ether bond (—O—), a linear or branched alkylene group, an aromatic hydrocarbon group, or a combination thereof. Among these, the group other than the polymerizable group is more preferably an ester bond [—C(═O)—O—, —O—C(═O)—], an ether bond (—O—), a linear or branched alkylene group, or a combination thereof, and still more preferably an ether bond [—O—].

Among these, W¹ is preferably a group constituted of only a polymerizable group; or a group constituted of a polymerizable group and, as the group other than the polymerizable group, an ester bond [—C(═O)—O—, —O—C(═O)—], an ether bond (—O—), a linear or branched alkylene group, or a combination thereof, and more preferably a group constituted of only a polymerizable group.

In General Formula (a01-1), C^(t) represents a tertiary carbon atom. However, a carbon atom at an α-position of C constitutes a carbon-carbon unsaturated bond.

The “α-position of C^(t)” means the first carbon atom adjacent to the carbon atom (C) bonded to the oxy group (—O—) in General Formula (a01-1).

In General Formula (a01-1), R¹¹ represents an unsaturated hydrocarbon group which may have a substituent. However, a carbon atom at an α-position of C constitutes a carbon-carbon unsaturated bond.

Examples of the unsaturated hydrocarbon group as R¹¹ include an alkenyl group.

The linear alkenyl group as R¹¹ preferably has 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms, still more preferably 2 to 4 carbon atoms, and particularly preferably 3 carbon atoms. The alkenyl group as R¹¹ may be linear or branched. Examples of the linear alkenyl group include a vinyl group, a propenyl group (an allyl group), and a butynyl group. Examples of the branched alkenyl group include a 1-methylvinyl group, a 2-methylvinyl group, a 1-methylpropenyl group, 2-methylpropenyl group, and a 1-methyl-2-methylpropenyl group.

Examples of the substituent which the unsaturated hydrocarbon group as R¹¹ may have include an aromatic hydrocarbon group (a group in which one hydrogen atom has been removed from an aromatic hydrocarbon ring such as benzene, naphthalene, anthracene, or phenanthrene), a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, or the like), an alkoxy group (a methoxy group, an ethoxy group, a propoxy group, a butoxy group, or the like), and an alkyloxycarbonyl group.

In General Formula (a01-1), R¹² and R¹³ each independently represent a chain saturated hydrocarbon group which may have a substituent.

The chain saturated hydrocarbon group as R¹² and R¹³ may be linear or branched.

The linear saturated hydrocarbon group (the alkyl group) as R¹² and R¹³ preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, still more preferably 1 or 4 carbon atoms, and particularly preferably 1 or 2 carbon atoms. Specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n-pentyl group. Among these, a methyl group, an ethyl group, or an n-butyl group is preferable, and a methyl group or an ethyl group is more preferable.

The branched alkyl group as R¹² and R¹³ preferably has 3 to 10 carbon atoms and more preferably 3 to 5 carbon atoms. Specific examples thereof include an isopropyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a neopentyl group a 1,1-diethylpropyl group, and a 2,2-dimethylbutyl group. Among these, an isopropyl group is preferable.

Preferred examples of the constitutional unit (a01) include a constitutional unit represented by General Formula (a01-1-1).

[In the formula, R⁰¹ represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. C^(t) represents a tertiary carbon atom. Ra⁰⁰¹ to Ra⁰⁰³ each independently represents a hydrogen atom, a monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms, or a monovalent cyclic hydrocarbon group having 3 to 20 carbon atoms. Part or all of hydrogen atoms which the chain saturated hydrocarbon group and the cyclic hydrocarbon group have may be substituted with a substituent. R¹² and R¹³ each independently represent a chain saturated hydrocarbon group which may have a substituent].

In General Formula (a01-1-1), R⁰¹ represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. The alkyl group having 1 to 5 carbon atoms as R⁰¹ is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group.

The halogenated alkyl group having 1 to 5 carbon atoms as R⁰¹ is a group in which part or all of hydrogen atoms of the above-described alkyl group having 1 to 5 carbon atoms have been substituted with a halogen atom. The halogen atom is particularly preferably a fluorine atom.

R⁰¹ is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms, and in terms of industrial availability, more preferably a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, still more preferably a hydrogen atom or a methyl group, and particularly preferably a methyl group.

In General Formula (a01-1-1), C represents a tertiary carbon atom.

In General Formula (a01-1-1), Ra⁰⁰¹ to Ra⁰⁰³ each independently represents a hydrogen atom, a monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms, or a monovalent cyclic hydrocarbon group having 3 to 20 carbon atoms. Part or all of hydrogen atoms which the chain saturated hydrocarbon group and the cyclic hydrocarbon group have may be substituted with a substituent.

In General Formula (a01-1-1), examples of the monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms, as Ra⁰⁰¹ to Ra⁰⁰³, include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a decyl group.

Examples of the monovalent cyclic hydrocarbon group having 3 to 20 carbon atoms as Ra⁰⁰¹ to Ra⁰⁰³ include a monovalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms. Examples of the monovalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms include monocyclic aliphatic saturated hydrocarbon groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecyl group, and cyclododecyl group; and polycyclic aliphatic saturated hydrocarbon groups such as a bicyclo[2.2.2]octanyl group, a tricyclo[5.2.1.02,6]decanyl group, a tricyclo [3.3.1.13,7]decanyl group, a tetracyclo[6.2.1.13,6.02,7] dodecanyl group, and an adamantyl group.

From the viewpoint of easy synthesis of a monomer which provides a constitutional unit represented by General Formula (a01-1-1), among them, Ra⁰⁰¹ to Ra⁰⁰³ is preferably a hydrogen atom or a monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms, among the above, more preferably a hydrogen atom, a methyl group, or an ethyl group, and particularly preferably a hydrogen atom or a methyl group.

Examples of the substituent which the chain saturated hydrocarbon group or the cyclic hydrocarbon group represented by Ra⁰⁰¹ to Ra⁰⁰³ has include the same group as the substituent which the unsaturated hydrocarbon group as R¹¹ in General Formula (a01-1) described above may have.

Examples of the substituent in Ra⁰⁰¹ to Ra⁰⁰³ may have include an aromatic hydrocarbon group (a group in which one hydrogen atom has been removed from an aromatic hydrocarbon ring such as benzene, naphthalene, anthracene, or phenanthrene), a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, or the like), an alkoxy group (a methoxy group, an ethoxy group, a propoxy group, a butoxy group, or the like), and an alkyloxycarbonyl group.

In General Formula (a01-1-1), the description for R¹² and R¹³ is the same as the description for the chain saturated hydrocarbon group which may have a substituent, as R¹² and R¹³ in General Formula (a01-1), and a methyl group, an ethyl group, or an isopropyl group is more preferable.

Specific examples of the constitutional unit (a01) are as follows.

In each of the formulae shown below, R^(α) represents a hydrogen atom, a methyl group, or a trifluoromethyl group.

The constitutional unit (a01) that the component (A1) has may be one kind or may be two or more kinds.

Among the above, the constitutional unit (a01) is preferably at least one selected from the group consisting of the constitutional units represented by General Formula (a01-1-11) to (a01-1-16).

The proportion of the constitutional unit (a01) in the component (A1) is preferably 10% by mole or 80% by mole or less, more preferably 20% by mole or more and 70% by mole or less, and still more preferably 30% by mole or more and 60% by mole or less, with respect to the total amount (100% by mole) of all constitutional units constituting the component (A1).

In a case where the proportion of the constitutional unit (a01) is equal to or more than the lower limit of the preferred range described above, lithography characteristics such as sensitivity and roughness reduction are improved, and thus a resist pattern having high rectangularity is easily formed. On the other hand, in a case where the proportion of the constitutional unit (a01) is equal to or lower than the upper limit of the preferred range described above, balancing with other constitutional units is easy.

<<Constitutional Unit (a02)>>

The constitutional unit (a02) is a constitutional unit derived from a compound represented by General Formula (a02-1).

[In General Formula (a02-1), W² represents a polymerizable group-containing group. Wa² represents an aromatic hydrocarbon group. Part or all of hydrogen atoms which the aromatic hydrocarbon group has may be substituted with a substituent other than a hydroxy group. W² and Wa² may form a condensed ring. n2 represents an integer in a range of 1 to 3.]

In General Formula (a02-1), W² represents a polymerizable group-containing group.

The “polymerizable group” as W² is a group that enables a compound having the polymerizable group to be polymerized by radical polymerization or the like, and includes a group containing a multiple bond between carbon atoms, such as an ethylenic double bond.

Examples of the polymerizable group as W² include a vinyl group, an allyl group, acryloyl group, a methacryloyl group, a fluorovinyl group, a difluorovinyl group, a trifluorovinyl group, a difluorotrifluoromethylvinyl group, a trifluoroallyl group, a perfluoroallyl group, a trifluoromethylacryloyl group, a nonylfluorobutylacryloyl group, a vinyl ether group, a fluorine-containing vinyl ether group, an allyl ether group, a fluorine-containing allyl ether group, a styryl group, and a vinylnaphthyl group, a fluorine-containing styryl group, a fluorine-containing vinylnaphthyl group, a norbornyl group, a fluorine-containing norbornyl group, and a silyl group.

The “polymerizable group-containing group” as W² may be a group composed of only a polymerizable group, or a group composed of a polymerizable group and a group other than the polymerizable group. Examples of the group other than the polymerizable group include a divalent hydrocarbon group which may have a substituent and a divalent linking group containing a hetero atom.

Here, the divalent hydrocarbon group which may have a substituent and the divalent linking group containing a hetero atom are respectively the same as the divalent hydrocarbon group which may have a substituent and the divalent linking group containing a hetero atom, which are exemplified in the description for “polymerizable group-containing group” as W¹ in General Formula (a01-1) described above.

Among the above, the group other than the polymerizable group is preferably an ester bond [—C(═O)—O—, —O—C(═O)—], an ether bond (—O—), a linear or branched alkylene group, or a combination thereof, and more preferably an ester bond [—C(═O)—O—, —O—C(═O)—].

W² is preferably a group constituted of only a polymerizable group; or a group constituted of a polymerizable group and, as the group other than the polymerizable group, an ester bond [—C(═O)—O—, —O—C(═O)—], an ether bond (—O—), a linear or branched alkylene group, or a combination thereof, more preferably a group constituted of a polymerizable group and, as the group other than the polymerizable group, an ester bond [—C(═O)—O—, —O—C(═O)—] or an ether bond (—O—), still more preferably a group constituted of a vinyl group, an acryloyl group, or a methacryloyl group as the polymerizable group, and an ether bond (—O—) as the group other than the polymerizable group, and particularly preferably a vinyl group, an acryloyloxy group, or a methacryloyloxy group.

In General Formula (a02-1), Wa² represents an aromatic hydrocarbon group. Part or all of hydrogen atoms which the aromatic hydrocarbon group has may be substituted with a substituent other than a hydroxy group.

Examples of the aromatic hydrocarbon group as Wa² include a group in which (n2+1) hydrogen atoms have been removed from an aromatic ring. The aromatic ring is not particularly limited as long as it is a cyclic conjugated system having (4n+2) π electrons, and it may be monocyclic or polycyclic. The aromatic ring preferably has 5 to 30 carbon atoms, more preferably 5 to 20 carbon atoms, still more preferably 6 to 15 carbon atoms, and particularly preferably 6 to 12 carbon atoms. Specific examples of the aromatic ring include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; and an aromatic heterocyclic ring in which a part of carbon atoms constituting the above-described aromatic hydrocarbon ring have been substituted with a hetero atom. Examples of the hetero atom in the aromatic heterocyclic rings include an oxygen atom, a sulfur atom, and a nitrogen atom. Specific examples of the aromatic heterocyclic ring include a pyridine ring and a thiophene ring.

Examples of the substituent other than a hydroxy group, which Wa² may have, include a carboxy group, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, and the like), an alkoxy group (a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and the like), and an alkyloxycarbonyl group.

In General Formula (a02-1), W² and Wa² may form a condensed ring.

In a case where W² and Wa² form a condensed ring, examples of the ring structure of the condensed ring include a condensed ring of an alicyclic hydrocarbon and an aromatic hydrocarbon. The condensed ring formed by W² and Wa² may have a hetero atom.

The alicyclic hydrocarbon moiety in the condensed ring formed by W² and Wa² may be a monocyclic ring or a polycyclic ring.

Examples of the condensed ring formed by W² and Wa² include a condensed ring formed by a polymerizable group in W² moiety and by Wa², and a condensed ring formed by a group other than the polymerizable group in the W² moiety and by Wa².

The condensed ring formed by W² and Wa² may have a substituent.

Examples of this substituent include a methyl group, an ethyl group, propyl group, a hydroxy group, a hydroxyalkyl group, a carboxy group, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, and the like), an alkoxy group (a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and the like), an acyl group, an alkyloxycarbonyl group, and an alkyloxycarbonyloxy group.

Specific examples of the condensed ring formed by W² and Wa² are shown below. W^(α) represents a polymerizable group. ** represents a bond to a hydroxy group.

In General Formula (a02-1), n2 represents an integer in a range of 1 to 3, preferably 1 or 2, and more preferably 1.

Preferred examples of the constitutional unit (a02) include a constitutional unit represented by General Formula (a02-1-1) and a constitutional unit represented by General Formula (a02-1-2).

[In General Formula (a02-1-1), R⁰²¹ represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. Wa²¹ represents an aromatic hydrocarbon group. Part or all of hydrogen atoms which the aromatic hydrocarbon group has may be substituted with a substituent other than a hydroxy group. n21 represents an integer in a range of 1 to 3. [In General Formula (a02-1-2), R⁰⁰² represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. Wa²² represents an aromatic hydrocarbon group. Part or all of hydrogen atoms which the aromatic hydrocarbon group has may be substituted with a substituent other than a hydroxy group. n22 represents an integer in a range of 1 to 3.]

In General Formula (a02-1-1), R⁰²¹ represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. The alkyl group having 1 to 5 carbon atoms as R⁰²¹ is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group.

The halogenated alkyl group having 1 to 5 carbon atoms as R⁰²¹ is a group in which part or all of hydrogen atoms of the above-described alkyl group having 1 to 5 carbon atoms have been substituted with a halogen atom. The halogen atom is particularly preferably a fluorine atom.

R⁰²¹ is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms, and in terms of industrial availability, more preferably a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, still more preferably a hydrogen atom or a methyl group, and particularly preferably a hydrogen atom.

In General Formula (a02-1-1), Wa²¹ represents an aromatic hydrocarbon group. Part or all of hydrogen atoms which the aromatic hydrocarbon group has may be substituted with a substituent other than a hydroxy group. The description for Wa²¹ is the same as the description for Wa² in General Formula (a02-1) described above, and Wa²¹ is preferably a group in which (n21+1) hydrogen atoms have been removed from the aromatic hydrocarbon ring and more preferably a group in which (n21+1) hydrogen atoms have been removed from benzene or naphthalene.

In General Formula (a02-1-1), n21 represents an integer in a range of 1 to 3, preferably 1 or 2, and more preferably 1.

In General Formula (a02-1-2), R⁰²² represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms.

The alkyl group having 1 to 5 carbon atoms as R⁰²² is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group.

The halogenated alkyl group having 1 to 5 carbon atoms as R⁰²² is a group in which part or all of hydrogen atoms of the above-described alkyl group having 1 to 5 carbon atoms have been substituted with a halogen atom. The halogen atom is particularly preferably a fluorine atom.

R⁰²² is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms, and in terms of industrial availability, more preferably a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, still more preferably a hydrogen atom or a methyl group, and particularly preferably a methyl group.

In General Formula (a02-1-2), Wa²² represents an aromatic hydrocarbon group. Part or all of hydrogen atoms which the aromatic hydrocarbon group has may be substituted with a substituent other than a hydroxy group. The description for Wa²² is the same as the description for Wa² in General Formula (a02-1) described above, and Wa²² is preferably a group in which (n22+1) hydrogen atoms have been removed from the aromatic hydrocarbon ring and more preferably a group in which (n22+1) hydrogen atoms have been removed from benzene or naphthalene.

In General Formula (a02-1-2), n22 represents an integer in a range of 1 to 3, preferably 1 or 2, and more preferably 1.

Specific examples of the constitutional unit (a02) are shown below.

In each of the formulae shown below, R^(α) represents a hydrogen atom, a methyl group, or a trifluoromethyl group.

The constitutional unit (a02) that the component (A1) has may be one kind or may be two or more kinds.

Among the above, the constitutional unit (a02) is preferably at least one selected from the group consisting of constitutional units respectively represented by General Formulae (a02-1-11) to (a02-1-33), more preferably at least one selected from the group consisting of constitutional units respectively represented by General Formulae (a02-1-11) to (a02-1-14), (a02-1-19) to (a02-1-22), and (a02-1-25), and still more preferably at least one selected from the group consisting of constitutional units respectively represented by General Formulae (a02-1-11), (a02-1-19), and (a02-1-25).

The proportion of the constitutional unit (a02) in the component (A1) is preferably 20% by mole or 90% by mole or less, more preferably 30% by mole or more and 80% by mole or less, and still more preferably 40% by mole or more and 70% by mole or less, with respect to the total amount (100% by mole) of all constitutional units constituting the component (A1).

In a case where the proportion of the constitutional unit (a02) is equal to or more than the lower limit of the preferred range described above, lithography characteristics such as sensitivity and roughness reduction are improved, and thus a resist pattern having high rectangularity is easily formed. On the other hand, in a case where the proportion of the constitutional unit (a02) is equal to or lower than the upper limit of the preferred range described above, balancing with other constitutional units is easy.

<<Other Constitutional Units>>

The component (A1) may have other constitutional units as necessary in addition to the constitutional unit (a01) and the constitutional unit (a02). Examples of other constitutional units include a constitutional unit (a1) containing an acid-decomposable group having a polarity which is increased by action of an acid (provided that a constitutional unit corresponding to the constitutional unit (a01) is excluded); a constitutional unit (a2) containing a lactone-containing cyclic group, a —SO₂-containing cyclic group, or a carbonate-containing cyclic group (provided that a constitutional unit corresponding to the constitutional unit (a01) or the constitutional unit (a1) is excluded); a constitutional unit (a3) containing a polar group-containing aliphatic hydrocarbon group (provided that a constitutional unit corresponding to the constitutional unit (a01), the constitutional unit (a1), or the constitutional unit (a2) is excluded); a constitutional unit (a4) containing an acid non-dissociable aliphatic cyclic group; and a constitutional unit (st) derived from styrene or a derivative thereof.

In regard to constitutional unit (a1):

The component (A1) may further have the constitutional unit (a1) in addition to the constitutional unit (a01) and the constitutional unit (a02).

The component (a1) is a constitutional unit (provided that a constitutional unit corresponding to the constitutional unit (a01) is excluded) containing an acid-decomposable group having polarity which is increased by action of an acid.

Examples of the acid-dissociable group constituting an acid-decomposable group are the same as those which have been proposed as acid-dissociable groups for the base resin for a chemical amplification-type resist composition.

Specific examples of acid-dissociable groups of the base resin proposed for a chemical amplification-type resist composition contains an “acetal-type acid-dissociable group”, a “tertiary alkyl ester-type acid-dissociable group”, and a “tertiary alkyloxycarbonyl acid-dissociable group” described below.

Acetal-Type Acid-Dissociable Group:

Examples of the acid-dissociable group for protecting a carboxy group or a hydroxy group as a polar group include the acid-dissociable group represented by General Formula (a1-r-1) shown below (hereinafter, also referred to as an “acetal-type acid-dissociable group”).

[In the formula, Ra′¹ to Ra′² represent hydrogen atoms or alkyl groups. Ra′³ represents a hydrocarbon group, and Ra′³ may be bonded to Ra′¹ or Ra′² to form a ring.]

In General Formula (a1-r-1), it is preferable that at least one of Ra′¹ and Ra′² represent a hydrogen atom and more preferable that both Ra′¹ and Ra′² represent hydrogen atoms.

In a case where Ra′¹ or Ra′² represents an alkyl group, the alkyl group preferably an alkyl group having 1 to 5 carbon atoms. Specific examples thereof preferably include a linear or branched alkyl group. More specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. Among these, a methyl group or an ethyl group is preferable, and a methyl group is particularly preferable.

In General Formula (a1-r-1), examples of the hydrocarbon group as Ra′³ include a linear or branched alkyl group and a cyclic hydrocarbon group.

The linear alkyl group preferably has 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms, and still more preferably 1 or 2 carbon atoms. Specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n-pentyl group. Among these, a methyl group, an ethyl group, or an n-butyl group is preferable, and a methyl group or an ethyl group is more preferable.

The branched alkyl group preferably has 3 to 10 carbon atoms and more preferably 3 to 5 carbon atoms. Specific examples thereof include an isopropyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a neopentyl group a 1,1-diethylpropyl group, and a 2,2-dimethylbutyl group. Among these, an isopropyl group is preferable.

In a case where Ra′³ represents a cyclic hydrocarbon group, the cyclic hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group and may be a polycyclic group or a monocyclic group.

The aliphatic hydrocarbon group which is a monocyclic group is preferably a group in which one hydrogen atom has been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane.

The aliphatic hydrocarbon group which is a polycyclic group is preferably a group in which one hydrogen atom has been removed from a polycycloalkane. The polycycloalkane preferably has 7 to 12 carbon atoms, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

In a case where the cyclic hydrocarbon group as Ra′³ is an aromatic hydrocarbon group, the aromatic hydrocarbon group is a hydrocarbon group having at least one aromatic ring.

The aromatic ring is not particularly limited as long as it is a cyclic conjugated system having (4n+2) π electrons, and may be monocyclic or polycyclic. The aromatic ring preferably has 5 to 30 carbon atoms, more preferably 5 to 20 carbon atoms, still more preferably 6 to 15 carbon atoms, and particularly preferably 6 to 12 carbon atoms. Specific examples of the aromatic ring include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; and an aromatic heterocyclic ring in which a part of carbon atoms constituting the above-described aromatic hydrocarbon ring have been substituted with a hetero atom. Examples of the hetero atom in the aromatic heterocyclic rings include an oxygen atom, a sulfur atom, and a nitrogen atom. Specific examples of the aromatic heterocyclic ring include a pyridine ring and a thiophene ring.

Specific examples of the aromatic hydrocarbon group as Ra′³ include a group in which one hydrogen atom has been removed from the above-described aromatic hydrocarbon ring or aromatic heterocyclic ring (an aryl group or a heteroaryl group); a group in which one hydrogen atom has been removed from an aromatic compound having two or more aromatic rings (biphenyl, fluorene or the like); and a group in which one hydrogen atom of the above-described aromatic hydrocarbon ring or aromatic heterocyclic ring has been substituted with an alkylene group (an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethyl group). The number of carbon atoms in the alkylene group bonded to the aromatic hydrocarbon ring or aromatic heterocyclic ring is preferably in a range of 1 to 4, more preferably 1 or 2, and particularly preferably 1.

The cyclic hydrocarbon group in Ra′³ may have a substituent. Examples of the substituent include, —R^(P1), —R^(P2)—O—R^(P1), —R^(P2)—CO—R^(P1), —R^(P2)—CO—OR^(P1), —R^(P2)—O—CO—R^(P1), —R^(P2)—OH, —R^(P2)—CN, and —R^(P2)—COOH (hereinafter, these substituents are also collectively referred to as “Ra^(x5)). Here, R^(P1) represents a monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms, a monovalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms. In addition, R^(P2) represents a single bond, a divalent chain saturated hydrocarbon group having 1 to 10 carbon atoms, a divalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms. However, part or all of the hydrogen atoms included in the chain saturated hydrocarbon group, the aliphatic cyclic saturated hydrocarbon group, and the aromatic hydrocarbon group of R^(P1) and R^(P2) may be substituted with a fluorine atom. In the aliphatic cyclic hydrocarbon group, one or more of the above-described substituents may be included as a single kind, or one or more of the above-described substituents may be included as a plurality of kinds.

Examples of the monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a decyl group.

Examples of the monovalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms include monocyclic aliphatic saturated hydrocarbon groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecyl group, and cyclododecyl group; and polycyclic aliphatic saturated hydrocarbon groups such as a bicyclo[2.2.2]octanyl group, a tricyclo[5.2.1.02,6]decanyl group, a tricyclo [3.3.1.13,7]decanyl group, a tetracyclo[6.2.1.13,6.02,7] dodecanyl group, and an adamantyl group.

Examples of the monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms include a group in which one hydrogen atom has been removed from an aromatic hydrocarbon ring such as benzene, biphenyl, fluorene, naphthalene, anthracene, or phenanthrene.

In a case where Ra′³ is bonded to Ra′¹ or Ra′² to form a ring, the cyclic group is preferably a 4- to 7-membered ring, and more preferably a 4- to 6-membered ring. Specific examples of the cyclic group include a tetrahydropyranyl group and a tetrahydrofuranyl group.

Tertiary Alkyl Ester-Type Acid-Dissociable Group:

Among the above polar groups, examples of the acid-dissociable group for protecting the carboxy group include the acid-dissociable group represented by General Formula (a1-r-2) shown below.

Among the acid-dissociable groups represented by General Formula (a1-r-2), for convenience, a group which is constituted of alkyl groups is referred to as a “tertiary alkyl ester-type acid-dissociable group”.

[In the formula, Ra′⁴ to Ra′⁶ each represents a hydrocarbon group, and Ra′⁵ and Ra′⁶ may be bonded to each other to form a ring.]

Examples of the hydrocarbon group as Ra′⁴ include a linear or branched alkyl group, a chain or cyclic alkenyl group, or a cyclic hydrocarbon group.

The linear or branched alkyl group and the cyclic hydrocarbon group (an aliphatic hydrocarbon group which is a monocyclic group, an aliphatic hydrocarbon group which is a polycyclic group, or an aromatic hydrocarbon group) as Ra′⁴ are the same as those mentioned as Ra′³ described above.

The chain or cyclic alkenyl group as Ra′⁴ is preferably an alkenyl group having 2 to 10 carbon atoms.

Examples of the hydrocarbon groups as Ra′⁵ and Ra′⁶ include the same groups as those mentioned above as Ra′³.

In a case where Ra′⁵ to Ra′⁶ are bonded to each other to form a ring, groups represented by General Formula (a1-r2-1), General Formula (a1-r2-2), and General Formula (a1-r2-3) can be suitably mentioned.

On the other hand, in a case where Ra′⁴ to Ra′⁶ are not bonded to each other and represent an independent hydrocarbon group, a group represented by General Formula (a1-r2-4) can be suitably mentioned.

[In General Formula (a1-r2-1), Ra′¹⁰ represents a linear or branched alkyl group having 1 to 12 carbon atoms, a part of which may be substituted with a halogen atom or a hetero atom-containing group. Ra′¹¹ represents a group that forms an aliphatic cyclic group together with a carbon atom to which Ra′¹⁰ is bonded. In General Formula (a1-r2-2), Ya represents a carbon atom. Xa is a group that forms a cyclic hydrocarbon group together with Ya. Part or all of the hydrogen atoms which the cyclic hydrocarbon group has may be substituted. Ra¹⁰¹ to Ra¹⁰³ each independently represents a hydrogen atom, a monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms, or a monovalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms. Part or all of the hydrogen atoms which the chain saturated hydrocarbon group and the aliphatic cyclic saturated hydrocarbon group have may be substituted. Two or more of Ra¹⁰¹ to Ra¹⁰³ may be bonded to each other to form a cyclic structure. In General Formula (a1-r2-3), Yaa represents a carbon atom. Xaa is a group that forms an aliphatic cyclic group together with Yaa. Ra¹⁰⁴ represents an aromatic hydrocarbon group which may have a substituent. In General Formula (a1-r2-4), Ra′¹² and Ra′¹³ each independently represent a monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms or a hydrogen atom. Part or all of the hydrogen atoms which the chain saturated hydrocarbon group has may be substituted. Ra′¹⁴ represents a hydrocarbon group which may have a substituent. * represents a bond.]

In General Formula (a1-r2-1), Ra′¹² represents a linear or branched alkyl group having 1 to 12 carbon atoms, a part of which may be substituted with a halogen atom or a hetero atom-containing group.

The linear alkyl group as Ra′¹² has 1 to 12 carbon atoms, and preferably has 1 to 10 carbon atoms and particularly preferably 1 to 5 carbon atoms.

Examples of the branched alkyl group as Ra′¹⁰ are the same as those mentioned above as Ra′³.

A part of the alkyl group as Ra′¹⁰ may be substituted with a halogen atom or a hetero atom-containing group. For example, a part of the hydrogen atoms constituting the alkyl group may be substituted with a halogen atom or a hetero atom-containing group. Further, a part of carbon atoms (such as methylene group) constituting the alkyl group may be substituted with a hetero atom-containing group.

Examples of the hetero atom mentioned here include an oxygen atom, a sulfur atom, and a nitrogen atom. Examples of the hetero atom-containing group include —O—, —C(═O)—O—, —O—C(═O)—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH—, —S—, —S(═O)₂—, and —S(═O)₂—O—.

In General Formula (a1-r2-1), Ra′¹¹ (an aliphatic cyclic group that is formed together with the carbon atom to which Ra′¹⁰ is bonded) is preferably the group mentioned as the aliphatic hydrocarbon group (alicyclic hydrocarbon group) which is a monocyclic group or a polycyclic group as Ra′³ in General Formula (a1-r-1). Among them, a monocyclic alicyclic hydrocarbon group is preferable, and specifically, a cyclopentyl group and a cyclohexyl group are more preferable, and a cyclopentyl group is still more preferable.

In General Formula (a1-r2-2), examples of the cyclic hydrocarbon group formed by Xa together with Ya include a group in which one or more hydrogen atoms are further removed from a cyclic monovalent hydrocarbon group (an aliphatic hydrocarbon group) as Ra′³ in General Formula (a1-r-1).

The cyclic hydrocarbon group which is formed by Xa together with Ya may have a substituent. Examples of these substituents include the same groups as the substituents which the cyclic hydrocarbon group as Ra′³ may have.

In General Formula (a1-r2-2), as Ra¹⁰¹ to Ra¹⁰³, examples of the monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a decyl group.

Examples of the monovalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms, as Ra¹⁰¹ to Ra¹⁰³, include monocyclic aliphatic saturated hydrocarbon groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecyl group, and cyclododecyl group; and polycyclic aliphatic saturated hydrocarbon groups such as a bicyclo[2.2.2]octanyl group, a tricyclo[5.2.1.02,6]decanyl group, a tricyclo[3.3.1.13,7]decanyl group, a tetracyclo[6.2.1.13,6.02,7] dodecanyl group, and an adamantyl group.

Among them, Ra¹⁰¹ to Ra¹⁰³ are preferably a hydrogen atom or a monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms, and among them, a hydrogen atom, a methyl group, and an ethyl group are more preferable, and a hydrogen atom is particularly preferable from the viewpoint of easy synthesis.

Examples of the substituent which the chain saturated hydrocarbon group represented by Ra¹⁰¹ to Ra¹⁰³ or the aliphatic cyclic saturated hydrocarbon group has include the same groups as Ra^(x5) described above.

Examples of the group containing a carbon-carbon double bond generated by forming a cyclic structure, in which two or more of Ra¹⁰¹ to Ra¹⁰³ are bonded to each other, include a cyclopentenyl group, a cyclohexenyl group, a methylcyclopentenyl group, a methylcyclohexenyl group, a cyclopentylideneethenyl group, and a cyclohexylideneethenyl group. Among these, a cyclopentenyl group, a cyclohexenyl group, and a cyclopentylideneethenyl group are preferable from the viewpoint of easy synthesis.

In General Formula (a1-r2-3), an aliphatic cyclic group that is formed by Xaa together with Yaa is preferably the group mentioned as the aliphatic hydrocarbon group which is a monocyclic group or a polycyclic group as Ra′³ in General Formula (a1-r-1).

In General Formula (a1-r2-3), Examples of the aromatic hydrocarbon group as Ra¹⁰⁴ include a group in which one or more hydrogen atoms have been removed from an aromatic hydrocarbon ring having 5 to 30 carbon atoms. Among them, Ra¹⁰⁴ is preferably a group in which one or more hydrogen atoms have been removed from an aromatic hydrocarbon ring having 6 to 15 carbon atoms, more preferably a group in which one or more hydrogen atoms have been removed from benzene, naphthalene, anthracene, or phenanthrene, still more preferably a group in which one or more hydrogen atoms have been removed from benzene, naphthalene, or anthracene, particularly preferably a group in which one or more hydrogen atoms have been removed from benzene or naphthalene, and most preferably a group in which one or more hydrogen atoms have been removed from benzene.

Examples of the substituent which Ra¹⁰⁴ in General Formula (a1-r2-3) may have include a methyl group, an ethyl group, propyl group, a hydroxy group, a carboxy group, a halogen atom, an alkoxy group (a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and the like), and an alkyloxycarbonyl group.

In General Formula (a1-r2-4), Ra′¹² and Ra′¹³ each independently represent a monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms or a hydrogen atom. Examples of the monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms as Ra′¹² and Ra′¹³ include the same monovalent chain saturated hydrocarbon groups as those having 1 to 10 carbon atoms as Ra¹⁰¹ to Ra¹⁰³ as described above. Part or all of the hydrogen atoms which the chain saturated hydrocarbon group has may be substituted.

Among them, Ra′¹² and Ra′¹³ are preferably a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms, still more preferably a methyl group or an ethyl group, and particularly preferably a methyl group.

In a case where the chain saturated hydrocarbon groups represented by Ra′¹² and Ra′¹³ are substituted, examples of the substituent include the same group as Ra^(x5) described above.

In General Formula (a1-r2-4), Ra′¹⁴ represents a hydrocarbon group which may have a substituent. Examples of the hydrocarbon group as Ra′¹⁴ include a linear or branched alkyl group and a cyclic hydrocarbon group.

The linear alkyl group as Ra′¹⁴ preferably has 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms, and still more preferably 1 or 2 carbon atoms. Specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n-pentyl group. Among these, a methyl group, an ethyl group, or an n-butyl group is preferable, and a methyl group or an ethyl group is more preferable.

The branched alkyl group as Ra′¹⁴ preferably has 3 to 10 carbon atoms and more preferably 3 to 5 carbon atoms. Specific examples thereof include an isopropyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a neopentyl group a 1,1-diethylpropyl group, and a 2,2-dimethylbutyl group. Among these, an isopropyl group is preferable.

In a case where Ra′¹⁴ represents a cyclic hydrocarbon group, the cyclic hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group and may be a polycyclic group or a monocyclic group.

The aliphatic hydrocarbon group which is a monocyclic group is preferably a group in which one hydrogen atom has been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane.

The aliphatic hydrocarbon group which is a polycyclic group is preferably a group in which one hydrogen atom has been removed from a polycycloalkane. The polycycloalkane preferably has 7 to 12 carbon atoms, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

Examples of the aromatic hydrocarbon group as Ra′¹⁴ include the same group as the aromatic hydrocarbon group as Ra¹⁰⁴. Among them, Ra′¹⁴ is preferably a group in which one or more hydrogen atoms have been removed from an aromatic hydrocarbon ring having 6 to 15 carbon atoms, more preferably a group in which one or more hydrogen atoms have been removed from benzene, naphthalene, anthracene, or phenanthrene, still more preferably a group in which one or more hydrogen atoms have been removed from benzene, naphthalene, or anthracene, particularly preferably a group in which one or more hydrogen atoms have been removed from naphthalene or anthracene, and most preferably a group in which one or more hydrogen atoms have been removed from naphthalene.

Examples of the substituent which may be included in Ra′¹⁴ include the same group as the substituent which may be included in Ra⁰⁴.

In a case where Ra′¹⁴ in General Formula (a1-r2-4) is a naphthyl group, the position at which the tertiary carbon atom in General Formula (a1-r2-4) is bonded is any one of the 1- or the 2-position of the naphthyl group.

In a case where Ra′¹⁴ in General Formula (a1-r2-4) is an anthryl group, the position at which the tertiary carbon atom in General Formula (a1-r2-4) is bonded is any one of the 1-, the 2-, or the 9-position of the anthryl group.

Specific examples of the group represented by General Formula (a1-r2-1) are shown below.

Specific examples of the group represented by General Formula (a1-r2-2) are shown below.

Specific examples of the group represented by General Formula (a1-r2-3) are shown below.

Specific examples of the group represented by General Formula (a1-r2-4) are shown below.

Tertiary Alkyloxycarbonyl Acid-Dissociable Group:

Among the polar groups, examples of the acid-dissociable group for protecting a hydroxy group include an acid-dissociable group (hereinafter, for convenience, also referred to as a “tertiary alkyloxycarbonyl acid-dissociable group”) represented by General Formula (a1-r-3) shown below.

[In the formula, Ra′⁷ to Ra′⁹ each represents an alkyl group.]

In General Formula (a1-r-3), Ra′⁷ to Ra′⁹ are each preferably an alkyl group having 1 to 5 carbon atoms and more preferably an alkyl group having 1 to 3 carbon atoms.

Further, the total number of carbon atoms in each alkyl group is preferably in a range of 3 to 7, more preferably in a range of 3 to 5, and most preferably 3 or 4.

Examples of the constitutional unit (a1) include a constitutional unit derived from acrylic acid ester in which the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent; a constitutional unit derived from acrylamide; a constitutional unit in which at least a part of hydrogen atoms in a hydroxy group of a constitutional unit derived from hydroxystyrene or a hydroxystyrene derivative are protected by the substituent including an acid-decomposable group; and a constitutional unit in which at least a part of hydrogen atoms in —C(═O)—OH of a constitutional unit derived from vinylbenzoic acid or a vinylbenzoic acid derivative are protected by the substituent including an acid-decomposable group.

Among the above, the constitutional unit (a1) is preferably a constitutional unit derived from acrylic acid ester in which the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent. Preferred specific examples of the constitutional unit (a1) include constitutional units represented by General Formula (a1-1) or (a1-2).

[In the formula, R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. Va¹ represents a divalent hydrocarbon group which may have an ether bond. n_(a1) represents an integer in a range of 0 to 2. Ra¹ is an acid-dissociable group represented by General Formula (a1-r-1) or (a1-r-2). Wa¹ represents an (n_(a2)+1)-valent hydrocarbon group, n_(a2) represents an integer in a range of 1 to 3, and Ra² represents an acid-dissociable group represented by General Formula (a1-r-1) or (a1-r-3).]

In General Formula (a1-1), the alkyl group having 1 to 5 carbon atoms as R is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. The halogenated alkyl group having 1 to 5 carbon atoms is a group in which part or all of hydrogen atoms in the alkyl group having 1 to 5 carbon atoms have been substituted with a halogen atom. The halogen atom is particularly preferably a fluorine atom.

R is preferably hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms, and most preferably a hydrogen atom or a methyl group in terms of industrial availability.

In General Formula (a1-1), the divalent hydrocarbon group as Va¹ may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group.

The aliphatic hydrocarbon group as the divalent hydrocarbon group represented by Va¹ may be saturated or unsaturated. In general, it is preferable that the aliphatic hydrocarbon group be saturated.

Specific examples of the aliphatic hydrocarbon group include a linear or branched aliphatic hydrocarbon group, and an aliphatic hydrocarbon group containing a ring in the structure thereof.

The linear aliphatic hydrocarbon group described above preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbon atoms. The linear aliphatic hydrocarbon group is preferably a linear alkylene group, and specific examples thereof include a methylene group [—CH₂—], an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], a tetramethylene group [—(CH₂)₄—], and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group described above preferably has 2 to 10 carbon atoms, more preferably 3 to 6 carbon atoms, still more preferably 3 or 4 carbon atoms, and most preferably 3 carbon atoms. The branched aliphatic hydrocarbon group is preferably a branched alkylene group, and specific examples thereof include alkylalkylene groups, for example, alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—; alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; and alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and —CH₂CH(CH₃)CH₂CH₂—. The alkyl group in the alkylalkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

Examples of the aliphatic hydrocarbon group containing a ring in the structure thereof include an alicyclic hydrocarbon group (a group in which two hydrogen atoms have been removed from an aliphatic hydrocarbon ring), a group in which the alicyclic hydrocarbon group is bonded to the terminal of the linear or branched aliphatic hydrocarbon group, and a group in which the alicyclic hydrocarbon group is interposed in the linear or branched aliphatic hydrocarbon group. The linear or branched aliphatic hydrocarbon group is the same as that defined for the above-described linear aliphatic hydrocarbon group or the above-described branched aliphatic hydrocarbon group.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms and more preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be monocyclic or polycyclic. The monocyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a polycycloalkane, and the polycycloalkane is preferably a group having 7 to 12 carbon atoms. Specific examples of the polycycloalkane include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

The aromatic hydrocarbon group as the divalent hydrocarbon group represented by Va¹ is a hydrocarbon group having an aromatic ring.

The aromatic hydrocarbon group preferably has 3 to 30 carbon atoms, more preferably 5 to 30 carbon atoms, still more preferably 5 to 20 carbon atoms, particularly preferably 6 to 15 carbon atoms, and most preferably 6 to 12 carbon atoms. Here, the number of carbon atoms in a substituent is not included in the number of carbon atoms. Specific examples of the aromatic ring which the aromatic hydrocarbon group has include aromatic hydrocarbon rings such as benzene, biphenyl, fluorene, naphthalene, anthracene, and phenanthrene; and aromatic heterocyclic rings in which a part of carbon atoms constituting the above-described aromatic hydrocarbon rings have been substituted with a hetero atom. Examples of the hetero atom in the aromatic heterocyclic rings include an oxygen atom, a sulfur atom, and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group include a group in which two hydrogen atoms have been removed from the above-described aromatic hydrocarbon ring (an arylene group); and a group in which one hydrogen atom of a group (an aryl group) formed by removing one hydrogen atom from the aromatic hydrocarbon ring has been substituted with an alkylene group (a group formed by removing one more hydrogen atom from an aryl group in arylalkyl groups such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethyl group). The alkylene group (an alkyl chain in the arylalkyl group) preferably has 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms, and particularly preferably 1 carbon atom.

In General Formula (a1-1), Ra¹ is an acid-dissociable group represented by General Formula (a1-r-1) or (a1-r-2).

In General Formula (a1-2), the (n_(a2)+1)-valent hydrocarbon group as Wa¹ may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aliphatic hydrocarbon group indicates a hydrocarbon group that has no aromaticity and may be saturated or unsaturated. In general, it is preferable that the aliphatic hydrocarbon group be saturated. Examples of the aliphatic hydrocarbon group include a linear or branched aliphatic hydrocarbon group, an aliphatic hydrocarbon group containing a ring in the structure thereof, and a combination of the linear or branched aliphatic hydrocarbon group and the aliphatic hydrocarbon group containing a ring in the structure thereof. The valency of (n_(a2)+1) is preferably divalent, trivalent, or tetravalent, and more preferably divalent or trivalent.

In General Formula (a1-2), Ra² is an acid-dissociable group represented by General Formula (a1-r-1) or (a1-r-3).

Specific examples of the constitutional unit represented by General Formula (a1-1) are shown below. In each of the formulae shown below, R^(α) represents a hydrogen atom, a methyl group, or a trifluoromethyl group.

The constitutional unit (a1) which the component (A1) has may be one kind or may be two or more kinds.

The constitutional unit (a1) is more preferably a constitutional unit represented by General Formula (a1-1) since lithography characteristics (sensitivity, shape, and the like) in lithography depending on an electron beam or EUV can be more easily increased.

The proportion of the constitutional unit (a1) in the component (A1) is preferably in a range of 5% to 50% by mole, more preferably in a range of 5% to 40% by mole, and still more preferably in a range of 10% to 30% by mole, with respect to the total amount (100% by mole) of all constitutional units constituting the component (A1).

In a case where the proportion of the constitutional unit (a1) is set within the preferred range described above, the efficiency of the deprotection reaction and the solubility of the developing solution is appropriately adjusted, and thus the effects according to the present invention can be more easily obtained.

In regard to constitutional unit (a2):

The component (A1) may further have the constitutional unit (a2) in addition to the constitutional unit (a01) and the constitutional unit (a02).

The component (a2) is a constitutional unit (provided that a constitutional unit corresponding to the constitutional unit (a01) or the constitutional unit (a1) is excluded) containing a lactone-containing cyclic group, a —SO₂-containing cyclic group, or a carbonate-containing cyclic group.

In a case where the component (A1) is used for forming a resist film, the lactone-containing cyclic group, the —SO₂-containing cyclic group, or the carbonate-containing cyclic group in the constitutional unit (a2) is effective for improving the adhesiveness of the resist film to the substrate. Further, due to having the constitutional unit (a2), lithography characteristics can be improved, for example, by the effects obtained by appropriately adjusting the acid diffusion length, increasing the adhesiveness of the resist film to the substrate, and appropriately adjusting the solubility during development.

The term “lactone-containing cyclic group” indicates a cyclic group that contains a ring (lactone ring) containing a —O—C(═O)— in the ring skeleton. In a case where the lactone ring is counted as the first ring and the group contains only the lactone ring, the group is referred to as a monocyclic group. Further, in a case where the group has other ring structures, the group is referred to as a polycyclic group regardless of the structures. The lactone-containing cyclic group may be a monocyclic group or a polycyclic group.

The lactone-containing cyclic group for the constitutional unit (a2) is not particularly limited, and any lactone-containing cyclic group may be used. Specific examples thereof include groups respectively represented by General Formulae (a2-r-1) to (a2-r-7) shown below.

[In the formulae, Ra′²¹s each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group, or a cyano group; R″ represents a hydrogen atom, an alkyl group, a lactone-containing cyclic group, a carbonate-containing cyclic group, or a —SO₂-containing cyclic group; A″ represents an oxygen atom, a sulfur atom, or an alkylene group having 1 to 5 carbon atoms, which may contain an oxygen atom (—O—) or a sulfur atom (—S—); and n′ represents an integer in a range of 0 to 2, and m′ is 0 or 1.]

In General Formulae (a2-r-1) to (a2-r-7), the alkyl group as Ra′²¹ is preferably an alkyl group having 1 to 6 carbon atoms. The alkyl group is preferably a linear alkyl group or a branched alkyl group. Specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, a neopentyl group, and a hexyl group. Among these, a methyl group or ethyl group is preferable, and a methyl group is particularly preferable.

The alkoxy group as Ra′²¹ is preferably an alkoxy group having 1 to 6 carbon atoms. Further, the alkoxy group is preferably a linear or branched alkoxy group. Specific examples of the alkoxy groups include a group formed by linking the above-described alkyl group mentioned as the alkyl group represented by Ra′²¹ to an oxygen atom (—O—).

The halogen atom as Ra′²¹ is preferably a fluorine atom.

Examples of the halogenated alkyl group as Ra′²¹ include groups in which part or all of hydrogen atoms in the above-described alkyl group as Ra′²¹ have been substituted with the above-described halogen atom. The halogenated alkyl group is preferably a fluorinated alkyl group and particularly preferably a perfluoroalkyl group.

In —COOR″ and —OC(═O)R″ as Ra′²¹, R″ represents a hydrogen atom, an alkyl group, a lactone-containing cyclic group, a carbonate-containing cyclic group, or a —SO₂-containing cyclic group.

The alkyl group as R″ may be linear, branched, or cyclic, and preferably has 1 to 15 carbon atoms.

In a case where R″ represents a linear or branched alkyl group, it is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms, and particularly preferably a methyl group or an ethyl group.

In a case where R″ represents a cyclic alkyl group, the cyclic alkyl group preferably has 3 to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and particularly preferably 5 to 10 carbon atoms. Specific examples thereof include a group in which one or more hydrogen atoms have been removed from a monocycloalkane, which may or may not be substituted with a fluorine atom or a fluorinated alkyl group; and a group in which one or more hydrogen atoms have been removed from polycycloalkanes such as bicycloalkane, tricycloalkane, or tetracycloalkane. More specific examples thereof include a group in which one or more hydrogen atoms have been removed from a monocycloalkane such as cyclopentane or cyclohexane; and a group in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane.

Examples of the lactone-containing cyclic group as R″ include the same groups as those respectively represented by General Formulae (a2-r-1) to (a2-r-7).

The carbonate-containing cyclic group as R″ has the same definition as that for the carbonate-containing cyclic group described below.

Specific examples of the carbonate-containing cyclic group include groups respectively represented by General Formulae (ax3-r-1) to (ax3-r-3).

The —SO₂-containing cyclic group as R″ has the same definition as that for the —SO₂-containing cyclic group described below. Specific examples thereof include groups respectively represented by General Formulae (a5-r-1) to (a5-r-4).

The hydroxyalkyl group as Ra′²¹ preferably has 1 to 6 carbon atoms, and specific examples thereof include a group in which at least one hydrogen atom in the alkyl group as Ra′²¹ has been substituted with a hydroxy group.

In General Formulae (a2-r-2), (a2-r-3) and (a2-r-5), as the alkylene group having 1 to 5 carbon atoms as A″, a linear or branched alkylene group is preferable, and examples thereof include a methylene group, an ethylene group, an n-propylene group, and an isopropylene group. Specific examples of the alkylene groups that contain an oxygen atom or a sulfur atom include groups in which —O— or —S— is interposed in the terminal of the alkylene group or between the carbon atoms of the alkylene group, and examples thereof include —O—CH₂—, —CH₂—O—CH₂—, —S—CH₂—, and —CH₂—S—CH₂—. A″ is preferably an alkylene group having 1 to 5 carbon atoms or —O—, more preferably an alkylene group having 1 to 5 carbon atoms, and most preferably a methylene group.

Specific examples of the groups respectively represented by General Formulae (a2-r-1) to (a2-r-7) are shown below.

The “—SO₂-containing cyclic group” indicates a cyclic group having a ring containing —SO₂— in the ring skeleton thereof. Specifically, the —SO₂-containing cyclic group is a cyclic group in which the sulfur atom (S) in —SO₂— forms a part of the ring skeleton of the cyclic group. In a case where the ring containing —SO₂— in the ring skeleton thereof is counted as the first ring and the group contains only the ring, the group is referred to as a monocyclic group. Further, in a case where the group has other ring structures, the group is referred to as a polycyclic group regardless of the structures. The —SO₂-containing cyclic group may be a monocyclic group or a polycyclic group. As the —SO₂-containing cyclic group, a cyclic group containing —O—SO₂— in the ring skeleton thereof, in other words, a cyclic group containing a sultone ring in which —O—S— in the —O—SO₂— group forms a part of the ring skeleton thereof is particularly preferable.

More specific examples of the —SO₂-containing cyclic group include groups respectively represented by General Formulae (a5-r-1) to (a5-r-4) shown below.

[In the formulae, Ra′⁵¹s each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group, or a cyano group; R″ represents a hydrogen atom, an alkyl group, a lactone-containing cyclic group, a carbonate-containing cyclic group, or a —SO₂-containing cyclic group; A″ represents an oxygen atom, a sulfur atom, or an alkylene group having 1 to 5 carbon atoms, which may contain an oxygen atom or a sulfur atom; and n′ represents an integer in a range of 0 to 2.]

In General Formulae (a5-r-1) and (a5-r-2), A″ has the same definition as that for A″ in General Formulae (a2-r-2), (a2-r-3) and (a2-r-5).

Examples of the alkyl group, the alkoxy group, the halogen atom, the halogenated alkyl group, —COOR″, —OC(═O)R″, and the hydroxyalkyl group as Ra′⁵¹ include the same groups as those described above in the explanation of Ra′²¹ in General Formulae (a2-r-1) to (a2-r-7).

Specific examples of the groups respectively represented by General Formulae (a5-r-1) to (a5-r-4) are shown below. In the formulae shown below, “Ac” represents an acetyl group.

The “carbonate-containing cyclic group” indicates a cyclic group having a ring (a carbonate ring) containing —O—C(═O)—O— in the ring skeleton thereof. In a case where the carbonate ring is counted as the first ring and the group contains only the carbonate ring, the group is referred to as a monocyclic group. Further, in a case where the group has other ring structures, the group is referred to as a polycyclic group regardless of the structures. The carbonate-containing cyclic group may be a monocyclic group or a polycyclic group.

The carbonate ring-containing cyclic group is not particularly limited, and any carbonate ring-containing cyclic group may be used. Specific examples thereof include groups respectively represented by General Formulae (ax3-r-1) to (ax3-r-3) shown below.

[In the formulae, Ra′^(x31)s each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group, or a cyano group; R″ represents a hydrogen atom, an alkyl group, a lactone-containing cyclic group, a carbonate-containing cyclic group, or a —SO₂-containing cyclic group; A″ represents an oxygen atom, a sulfur atom, or an alkylene group having 1 to 5 carbon atoms, which may contain an oxygen atom or a sulfur atom; and p′ represents an integer in a range of 0 to 3, and q′ is 0 or 1.]

In General Formulae (ax3-r-2) and (ax3-r-3), A″ has the same definition as that for A″ in General Formulae (a2-r-2), (a2-r-3) and (a2-r-5).

Examples of the alkyl group, the alkoxy group, the halogen atom, the halogenated alkyl group, —COOR″, —OC(═O)R″, and the hydroxyalkyl group as Ra′31 include the same groups as those described above in the explanation of Ra′²¹ in General Formulae (a2-r-1) to (a2-r-7).

Specific examples of the groups respectively represented by General Formulae (ax3-r-1) to (ax3-r-3) are shown below.

Among them, the constitutional unit (a2) is preferably a constitutional unit derived from acrylic acid ester in which the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent.

The constitutional unit (a2) is preferably a constitutional unit represented by General Formula (a2-1).

[In the formula, R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. Ya²¹ represents a single bond or a divalent linking group. La²¹ represents —O—, —COO—, —CON(R′)—, —OCO—, —CONHCO— or —CONHCS—, and R′ represents a hydrogen atom or a methyl group. However, in a case where La²¹ represents —O—, Ya²¹ does not represent —CO—. Ra²¹ represents a lactone-containing cyclic group, a carbonate-containing cyclic group, or a —SO₂-containing cyclic group.]

In General Formula (a2-1), R has the same definition as described above. R is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms and particularly preferably a hydrogen atom or a methyl group in terms of industrial availability.

In General Formula (a2-1), the divalent linking group as Ya²¹ is not particularly limited, and suitable examples thereof include a divalent hydrocarbon group which may have a substituent and a divalent linking group having a hetero atom.

Here, the divalent hydrocarbon group which may have a substituent and the divalent linking group containing a hetero atom are respectively the same as the divalent hydrocarbon group which may have a substituent and the divalent linking group containing a hetero atom, which are exemplified in the description for “polymerizable group-containing group” as W¹ in General Formula (a01-1) described above.

Among the above, Ya²¹ is preferably a single bond, an ester bond [—C(═O)—O—], an ether bond (—O—), a linear or branched alkylene group, or a combination thereof.

In General Formula (a2-1), Ra²¹ represents a lactone-containing cyclic group, a —SO₂-containing cyclic group, or a carbonate-containing cyclic group.

Suitable examples of the lactone-containing cyclic group, the —SO₂-containing cyclic group, and the carbonate-containing cyclic group as Ra²¹ include groups respectively represented by General Formulae (a2-r-1) to (a2-r-7), groups respectively represented by General Formulae (a5-r-1) to (a5-r-4), and groups respectively represented by General Formulae (ax3-r-1) to (ax3-r-3) described above. Among them, a lactone-containing cyclic group or a —SO₂-containing cyclic group is preferable, and groups respectively represented by General Formula (a2-r-1), (a2-r-2), (a2-r-6), or (a5-r-1) are more preferable. Specifically, anyone of groups respectively represented by Chemical Formulae (r-lc-1-1) to (r-lc-1-7), (r-lc-2-1) to (r-lc-2-18), (r-lc-6-1), (r-sl-1-1), and (r-sl-1-18) is more preferable.

The constitutional unit (a2) which the component (A1) has may be one kind or may be two or more kinds.

In a case where the component (A1) has the constitutional unit (a2), the proportion of the constitutional unit (a2) in the component (A1) is preferably in a range of 5% to 50% by mole, more preferably in a range of 5% to 40% by mole, and particularly preferably in a range of 10% to 30% by mole, with respect to the total amount (100% by mole) of all constitutional units constituting the component (A1).

In a case where the proportion of the constitutional unit (a2) is set within the preferred range described above, the effects of the present invention can be more easily obtained by appropriately adjusting the solubility of the developing solution or the like.

In regard to constitutional unit (a3):

The component (A1) may further have the constitutional unit (a3) in addition to the constitutional unit (a01) and the constitutional unit (a02).

The component (a3) is a constitutional unit (provided that a constitutional unit corresponding to the constitutional unit (a01), the constitutional unit (a1), or the constitutional unit (a2) is excluded) containing a polar group-containing aliphatic hydrocarbon group.

In a case where the component (A1) has the constitutional unit (a3), the hydrophilicity of the component (A) is increased, which contributes to an improvement in resolution. Further, acid diffusion length can be appropriately adjusted.

Examples of the polar group include a hydroxy group, a cyano group, a carboxy group, or a hydroxyalkyl group in which a part of hydrogen atoms of the alkyl group have been substituted with a fluorine atom, and the polar group is particularly preferably a hydroxy group.

Examples of the aliphatic hydrocarbon group include a linear or branched hydrocarbon group (preferably an alkylene group) having 1 to 10 carbon atoms, and a cyclic aliphatic hydrocarbon group (a cyclic group). The cyclic group may be a monocyclic group or a polycyclic group. For example, these cyclic groups can be suitably selected from a large number of groups that have been proposed in resins for a resist composition for an ArF excimer laser.

In a case where the cyclic group is a monocyclic group, the monocyclic group preferably has 3 to 10 carbon atoms. Among them, a constitutional unit derived from an acrylic acid ester that includes an aliphatic monocyclic group containing a hydroxy group, cyano group, carboxy group, or a hydroxyalkyl group in which a part of hydrogen atoms of the alkyl group have been substituted with a fluorine atom are particularly preferable. Examples of the monocyclic group include a group in which two or more hydrogen atoms have been removed from a monocycloalkane. Specific examples of the monocyclic group a include group in which two or more hydrogen atoms have been removed from a monocycloalkane such as cyclopentane, cyclohexane, or cyclooctane. Among these monocyclic groups, a group in which two or more hydrogen atoms have been removed from cyclopentane or a group in which two or more hydrogen atoms have been removed from cyclohexane are industrially preferable.

In a case where the cyclic group is a polycyclic group, the polycyclic group preferably has 7 to 30 carbon atoms. Among them, a constitutional unit derived from an acrylic acid ester that includes an aliphatic polycyclic group containing a hydroxy group, cyano group, carboxy group, or a hydroxyalkyl group in which a part of hydrogen atoms of the alkyl group have been substituted with a fluorine atom is particularly preferable. Examples of the polycyclic group include groups in which two or more hydrogen atoms have been removed from a bicycloalkane, tricycloalkane, tetracycloalkane, or the like. Specific examples thereof include a group in which two or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane. Among these polycyclic groups, a group in which two or more hydrogen atoms have been removed from adamantane, a group in which two or more hydrogen atoms have been removed from norbornane, or a group in which two or more hydrogen atoms have been removed from tetracyclododecane are industrially preferable.

The constitutional unit (a3) is not particularly limited, and any constitutional unit may be used as long as the constitutional unit contains a polar group-containing aliphatic hydrocarbon group.

The constitutional unit (a3) is a constitutional unit derived from acrylic acid ester in which the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent, and a constitutional unit containing a polar group-containing aliphatic hydrocarbon group is preferable.

In a case where the hydrocarbon group in the polar group-containing aliphatic hydrocarbon group is a linear or branched hydrocarbon group having 1 to 10 carbon atoms, the constitutional unit (a3) is preferably a constitutional unit derived from a hydroxyethyl ester of acrylic acid.

Further, preferred examples of the constitutional unit (a3) include a constitutional unit represented by General Formula (a3-1), a constitutional unit represented by General Formula (a3-2), and a constitutional unit represented by General Formula (a3-3) in a case where the hydrocarbon group in the polar group-containing aliphatic hydrocarbon group is a polycyclic group; and a constitutional unit represented by General Formula (a3-4) in a case where the hydrocarbon group is a monocyclic group.

[In the formulae, R has the same definition as described above, j represents an integer in a range of 1 to 3, k represents an integer in a range of 1 to 3, t′ represents an integer in a range of 1 to 3, 1 represents an integer in a range of 0 to 5, and s represents an integer in a range of 1 to 3.]

In General Formula (a3-1), j preferably represents 1 or 2 and more preferably 1. In a case where j represents 2, it is preferable that the hydroxy groups be bonded to the 3- and 5-positions of the adamantyl group. In a case where j represents 1, it is preferable that the hydroxy group be bonded to the 3-position of the adamantyl group. It is preferable that j represent 1, and it is particularly preferable that the hydroxy group be bonded to the 3-position of the adamantyl group.

In General Formula (a3-2), k preferably represents 1. The cyano group is preferably bonded to the 5- or 6-position of the norbornyl group.

In General Formula (a3-3), it is preferable that t′ represent 1. It is preferable that 1 represent 1. It is preferable that s represent 1. Further, it is preferable that a 2-norbornyl group or 3-norbornyl group be bonded to the terminal of the carboxy group of the acrylic acid. It is preferable that the fluorinated alkyl alcohol be bonded to the 5- or 6-position of the norbornyl group.

In General Formula (a3-4), t′ is preferably 1 or 2. l is preferably 0 or 1. s is preferably 1. It is preferable that the fluorinated alkyl alcohol be bonded to the 3- or 5-position of the cyclohexyl group.

The constitutional unit (a3) which the component (A1) has may be one kind or may be two or more kinds.

In a case where the component (A1) has the constitutional unit (a3), the proportion of the constitutional unit (a3) is preferably in a range of 1% to 30% by mole, more preferably in a range of 2% to 25% by mole, and still more preferably in a range of 5% to 20% by mole, with respect to the total amount (100% by mole) of all constitutional units constituting the component (A1).

In a case where the proportion of the constitutional unit (a3) is equal to or greater than the lower limit of the preferred range, the effect obtained by allowing the component (A1) to contain the constitutional unit (a3) can be sufficiently achieved by the effect described above. In a case where the proportion of the constitutional unit (a3) is equal to or lower than the upper limit of the preferred range, balance with other constitutional units can be obtained, and various lithography characteristics are improved.

In regard to constitutional unit (a4):

The component (A1) may further have the constitutional unit (a4) in addition to the constitutional unit (a01) and the constitutional unit (a02).

The constitutional unit (a4) is a constitutional unit containing an acid non-dissociable aliphatic cyclic group.

In a case where the component (A1) has the constitutional unit (a4), the dry etching resistance of the formed resist pattern is improved. Further, the hydrophobicity of the component (A) increases. The improvement in hydrophobicity contributes to the improvement in resolution, a resist pattern shape, and the like, particularly in the case of a solvent developing process.

The “acid non-dissociable cyclic group” in the constitutional unit (a4) is a cyclic group that remains in the constitutional unit without being dissociated even in a case where an acid acts thereto in a case where the acid is generated in the resist composition upon exposure (for example, in a case where the acid is generated from the constitutional unit generating an acid upon exposure or the component (B)).

Examples of the constitutional unit (a4) preferably include a constitutional unit derived from an acrylic acid ester including an acid non-dissociable aliphatic cyclic group. As the cyclic group, many cyclic groups conventionally known as cyclic groups used as a resin component of a resist composition for ArF excimer laser, KrF excimer laser (preferably ArF excimer laser), or the like can be used.

The cyclic group is particularly preferably at least one selected from a tricyclodecyl group, an adamantyl group, a tetracyclododecyl group, an isobornyl group, and a norbornyl group, from the viewpoint of industrial availability. These polycyclic groups may have, as a substituent, a linear or branched alkyl group having 1 to 5 carbon atoms.

Specific examples of the constitutional unit (a4) include constitutional units respectively represented by General Formulae (a4-1) to (a4-7).

[In the formula, R^(α) is the same as above.]

The constitutional unit (a4) which the component (A1) has may be one kind or may be two or more kinds.

In a case where the component (A1) has the constitutional unit (a4), the proportion of the constitutional unit (a4) is preferably in a range of 1% to 30% by mole and more preferably in a range of 5% to 20% by mole, with respect to the total amount (100% by mole) of all constitutional units constituting the component (A).

In a case where the proportion of the constitutional unit (a4) is equal to or greater than the lower limit of the preferred range, the effect obtained by allowing the component (A1) to contain the constitutional unit (a4) can be sufficiently achieved. In a case where the proportion of the constitutional unit (a4) is equal to or lower than the upper limit of the preferred range, the balance with other constitutional units is obtained easily.

In regard to constitutional unit (st):

The component (A1) may further have the constitutional unit (st) in addition to the constitutional unit (a01) and the constitutional unit (a02).

The constitutional unit (st) is a constitutional unit derived from styrene or a styrene derivative.

A “constitutional unit derived from styrene” means a constitutional unit that is formed by the cleavage of an ethylenic double bond of styrene. A “constitutional unit derived from a styrene derivative” means a constitutional unit (provided that a constitutional unit corresponding to the constitutional unit (a10) is excluded) formed by the cleavage of an ethylenic double bond of a styrene derivative.

The “styrene derivative” means a compound in which at least a part of hydrogen atoms of styrene are substituted with a substituent. Examples of the styrene derivative include a derivative in which the hydrogen atom at the α-position of styrene is substituted with a substituent, a derivative in which one or more hydrogen atoms of the benzene ring of styrene are substituted with a substituent, and a derivative in which the hydrogen atom at the α-position of styrene and one or more hydrogen atoms of the benzene ring are substituted with a substituent.

Examples of the substituent that is substituted for the hydrogen atom at the α-position of styrene include an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms.

The alkyl group having 1 to 5 carbon atoms is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group.

The halogenated alkyl group having 1 to 5 carbon atoms is a group in which part or all of hydrogen atoms in the alkyl group having 1 to 5 carbon atoms have been substituted with a halogen atom. The halogen atom is particularly preferably a fluorine atom.

The substituent that is substituted for the hydrogen atom at the α-position of styrene is preferably an alkyl group having 1 to 5 carbon atoms or a fluorinated alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms or a fluorinated alkyl group having 1 to 3 carbon atoms, and still more preferably a methyl group from the viewpoint of industrial availability.

Examples of the substituent that is substituted for the hydrogen atom of the benzene ring of styrene include an alkyl group, an alkoxy group, a halogen atom, and a halogenated alkyl group.

The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group is most preferable.

The alkoxy group as the substituent is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, or a tert-butoxy group, and still more preferably a methoxy group or an ethoxy group.

The halogen atom as the substituent is preferably a fluorine atom.

Examples of the halogenated alkyl group as the substituent include groups in which part or all of hydrogen atoms in the above-described alkyl groups have been substituted with the above-described halogen atom.

The substituent that is substituted for the hydrogen atom of the benzene ring of styrene is preferably an alkyl group having 1 to 5 carbon atoms, more preferably a methyl group or an ethyl group, and still more preferably a methyl group.

The constitutional unit (st) is preferably a constitutional unit derived from styrene or a constitutional unit derived from a styrene derivative in which the hydrogen atom at the α-position of styrene is substituted with an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms, more preferably a constitutional unit derived from styrene, or a constitutional unit derived from a styrene derivative in which the hydrogen atom at the α-position of styrene is substituted with a methyl group, and still more preferably a constitutional unit derived from styrene.

The constitutional unit (st) which the component (A1) has may be one kind or may be two or more kinds.

In a case where the component (A1) has the constitutional unit (st), the proportion of the constitutional unit (st) is preferably in a range of 1% to 30% by mole and more preferably in a range of 3% to 20% by mole with respect to the total amount (100% by mole) of all constitutional units constituting the component (A1).

The component (A1) contained in the resist composition may be used alone or in a combination of two or more kinds thereof.

In the resist composition according to the present embodiment, the component (A1) is a resin component containing the resin having the constitutional unit (a01) and the constitutional unit (a02).

Preferred examples of the component (A1) include a mixture of a high-molecular-weight compound having a repeated structure of the constitutional unit (a01) and a high-molecular-weight compound having a repeated structure of the constitutional unit (a02); and a copolymer having a repeated structure of the constitutional unit (a01) and the constitutional unit (a02).

Examples of the preferred component (A1) include a copolymer having a repeated structure of the constitutional unit (a01) and the constitutional unit (a02) The proportion of the constitutional unit (a01) in the copolymer having a repeated structure of the constitutional unit (a01) and the constitutional unit (a02) is preferably 20% by mole or more and 70% by mole or less, more preferably 30% by mole or more and 60% by mole or less, still more preferably 40% by mole or more and 55% by mole or less, with respect to the total amount (100% by mole) of all constitutional units constituting the copolymer. The proportion of the constitutional unit (a02) is preferably 30% by mole or more and 80% by mole or less, more preferably 40% by mole or more and 70% by mole or less, and still more preferably 45% by mole or more and 60% by mole or less, with respect to the total amount (100% by mole) of all constitutional units constituting the copolymer. In a case where the proportion of each constitutional unit is set within the preferred range described above, the effects of the present invention can be more easily obtained.

The component (A1) can be produced by dissolving, in a polymerization solvent, each monomer from which the constitutional unit is derived, adding thereto a radical polymerization initiator such as azobisisobutyronitrile (AIBN) or dimethyl azobisisobutyrate (for example, V-601) to perform polymerization.

Alternatively, the component (A1) can be produced by dissolving, in a polymerization solvent, a compound represented by General Formula (a01-1), a compound represented by General Formula (a02-1), and as necessary, a monomer from which a constitutional unit other than the constitutional unit (a01) and the constitutional unit (a02) is derived, and adding thereto a radical polymerization initiator such as described above to perform polymerization and then performing a deprotection reaction.

Further, a —C(CF₃)₂—OH group may be introduced into the terminal of the component (A1) during the polymerization using a chain transfer agent such as HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH in combination. As described above, a copolymer into which a hydroxyalkyl group, formed by substitution of a part of hydrogen atoms in the alkyl group with fluorine atoms, has been introduced is effective for reducing development defects and reducing line edge roughness (LER: uneven irregularities of a line side wall).

The weight-average molecular weight (Mw) (based on the polystyrene-equivalent value determined by gel permeation chromatography (GPC)) of the component (A1), which is not particularly limited, is preferably in a range of 1,000 to 50,000, more preferably in a range of 2,000 to 30,000, and still more preferably in a range of 3,000 to 20,000.

In a case where Mw of the component (A1) is equal to or lower than the upper limit of this preferred range, the resist composition exhibits sufficient solubility in a solvent for a resist such that the resist composition can be used as a resist composition. On the other hand, in a case where Mw of the component (A1) is equal to or greater than the lower limit of this preferred range, dry etching resistance and the cross-sectional shape of the resist pattern become excellent.

Further, the polydispersity (Mw/Mn) of the component (A1) is not particularly limited; however, it is preferably in a range of 1.0 to 4.0, more preferably in a range of 1.0 to 3.0, and particularly preferably in a range of 1.0 to 2.0. Mn represents the number-average molecular weight.

In regard to component (A2) In the resist composition according to the present embodiment, a base material component (hereinafter, referred to as a “component (A2)”) having solubility in a developing solution, which is changed by action of an acid, which does not correspond to the component (A1), may be used in combination as the component (A)

The component (A2) is not particularly limited and may be freely selected and used from a large number of conventionally known base material components for the chemical amplification-type resist composition.

As the component (A2), a high-molecular-weight compound or a low-molecular-weight compound may be used alone or in a combination of two or more kinds thereof.

The proportion of the component (A1) in the component (A) is preferably 25% by mass or greater, more preferably 50% by mass or greater, still more preferably 75% by mass or greater, and may be 100% by mass with respect to the total mass of the component (A). In a case where the proportion is 25% by mass or more, a resist pattern having various excellent lithography characteristics, such as high sensitivity, resolution, and roughness reduction, and having a good shape can be easily formed.

The content of the component (A) in the resist composition according to the present embodiment may be adjusted depending on the resist film thickness to be formed and the like.

<Component (B)>

In the resist composition according to the present embodiment, the acid generator component (B) is composed of a compound (B1) (hereinafter, also referred to as a “component (B1)”) having an anion moiety and a cation moiety.

Examples of the component (B1) include onium salt-based acid generators such as an iodonium salt and a sulfonium salt.

Examples of the onium salt-based acid generator in the component (B1) include a compound represented by General Formula (b-1) (hereinafter, also referred to as a “component (b-1)”), a compound represented by General Formula (b-2) (hereinafter, also referred to as a “component (b-2)”), and a compound represented by General Formula (b-3) (hereinafter, also referred to as a “component (b-3)”).

[In the formulae, R¹⁰¹ and R¹⁰⁴ to R¹⁰⁸ each independently represent a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent. R¹⁰⁴ and R¹⁰⁵ may be bonded to each other to form a ring structure. R¹⁰² represents a fluorinated alkyl group having 1 to 5 carbon atoms or a fluorine atom. Y¹⁰¹ represents a divalent linking group containing an oxygen atom or a single bond. V¹⁰¹ to V¹⁰³ each independently represents a single bond, an alkylene group, or a fluorinated alkylene group. L¹⁰¹ and L¹⁰² each independently represent a single bond or an oxygen atom. L¹⁰³ to L¹⁰⁵ each independently represents a single bond, —CO—, or —SO₂—. m represents an integer of 1 or greater, and M′^(m+) represents an m-valent onium cation.]

{Anion Moiety}

Anion in Component (b-1)

In General Formula (b-1), R¹⁰¹ represents a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent.

Cyclic group which may have substituent:

The cyclic group is preferably a cyclic hydrocarbon group, and the cyclic hydrocarbon group may be an aromatic hydrocarbon group or an aliphatic hydrocarbon group. The aliphatic hydrocarbon group indicates a hydrocarbon group that has no aromaticity. The aliphatic hydrocarbon group may be saturated or unsaturated. In general, it is preferable that the aliphatic hydrocarbon group be saturated.

The aromatic hydrocarbon group as R¹⁰¹ is a hydrocarbon group having an aromatic ring. The aromatic hydrocarbon group preferably has 3 to 30 carbon atoms, more preferably 5 to 30, still more preferably 5 to 20, particularly preferably 6 to 15, and most preferably 6 to 10. Here, the number of carbon atoms in a substituent is not included in the number of carbon atoms.

Specific examples of the aromatic ring the aromatic hydrocarbon group has as R¹⁰¹ include benzene, fluorene, naphthalene, anthracene, phenanthrene, biphenyl, or an aromatic heterocyclic ring in which some carbon atoms constituting any of these aromatic rings have been substituted with a hetero atom. Examples of the hetero atom in the aromatic heterocyclic rings include an oxygen atom, a sulfur atom, and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group as R¹⁰¹ include a group in which one hydrogen atom has been removed from the above-described aromatic ring (an aryl group such as a phenyl group or a naphthyl group) and a group in which one hydrogen atom in the aromatic ring has been substituted with an alkylene group (an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, 1-naphthylethyl group, or a 2-naphthylethyl group). The alkylene group (an alkyl chain in the arylalkyl group) preferably has 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms, and particularly preferably 1 carbon atom.

Examples of the cyclic aliphatic hydrocarbon group as R¹⁰¹ include aliphatic hydrocarbon groups containing a ring in the structure thereof.

Examples of the aliphatic hydrocarbon group containing a ring in the structure thereof include an alicyclic hydrocarbon group (a group in which one hydrogen atom has been removed from an aliphatic hydrocarbon ring), a group in which the alicyclic hydrocarbon group is bonded to the terminal of a linear or branched aliphatic hydrocarbon group, and a group in which the alicyclic hydrocarbon group is interposed in a linear or branched aliphatic hydrocarbon group.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms and more preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be a polycyclic group or a monocyclic group. The monocyclic alicyclic hydrocarbon group is preferably a group in which one or more hydrogen atoms have been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group in which one or more hydrogen atoms have been removed from a polycycloalkane, and the polycycloalkane preferably has 7 to 30 carbon atoms. Among them, the polycycloalkanes is preferably a polycycloalkane having a bridged ring-based polycyclic skeleton, such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane; or a polycycloalkane having a condensed ring-based polycyclic skeleton, such as a cyclic group having a steroid skeleton.

Among them, the cyclic aliphatic hydrocarbon group as R¹⁰¹ is preferably a group in which one or more hydrogen atoms have been removed from a monocycloalkane or a polycycloalkane, more preferably a group in which one hydrogen atom has been removed from a polycycloalkane, particularly preferably an adamantyl group or a norbornyl group, and most preferably an adamantyl group.

The linear aliphatic hydrocarbon group which may be bonded to the alicyclic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbon atoms. The linear aliphatic hydrocarbon group is preferably a linear alkylene group, and specific examples thereof include a methylene group [—CH₂—], an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], a tetramethylene group [—(CH₂)₄—], and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group which may be bonded to the alicyclic hydrocarbon group preferably has 2 to 10 carbon atoms, more preferably 3 to 6 carbon atoms, still more preferably 3 or 4 carbon atoms, and most preferably 3 carbon atoms. The branched aliphatic hydrocarbon group is preferably a branched alkylene group, and specific examples thereof include alkylalkylene groups, for example, alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—; alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; and alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and —CH₂CH(CH₃)CH₂CH₂—. The alkyl group in the alkylalkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

The cyclic hydrocarbon group as R¹⁰¹ may contain a hetero atom such as a heterocyclic ring. Specific examples thereof include lactone-containing cyclic groups respectively represented by General Formulae (a2-r-1) to (a2-r-7), —SO₂-containing cyclic groups respectively represented by General Formulae (a5-r-1) to (a5-r-4), and other heterocyclic groups respectively represented by Chemical Formulae (r-hr-1) to (r-hr-16). In the formulae, * represents a bond that is bonded to Y¹⁰¹ in General Formula (b-1).

Examples of the substituent of the cyclic group as R¹⁰¹ include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxy group, a carbonyl group, and a nitro group. The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group is most preferable.

The alkoxy group as the substituent is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, or a tert-butoxy group, and most preferably a methoxy group or an ethoxy group.

The halogen atom as the substituent is preferably a fluorine atom.

Examples of the above-described halogenated alkyl group as the substituent include a group in which part or all of hydrogen atoms in an alkyl group having 1 to 5 carbon atoms such as a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group have been substituted with the above-described halogen atom. The carbonyl group as a substituent is a group that is substituted for a methylene group (—CH₂—) constituting the cyclic hydrocarbon group.

The cyclic hydrocarbon group as R¹⁰¹ may be a condensed ring-type group containing a condensed ring in which an aliphatic hydrocarbon ring and an aromatic ring are condensed. Examples of the condensed ring include a condensed ring in which one or more aromatic rings are condensed with a polycycloalkane having a bridged ring-based polycyclic skeleton. Specific examples of the bridged ring-based polycycloalkane include bicycloalkanes such as bicyclo[2.2.1]heptane (norbornane) and bicyclo[2.2.2]octane. The condensed ring type is preferably a group containing a condensed ring in which two or three aromatic rings are condensed with a bicycloalkane and more preferably a group containing a condensed ring in which two or three aromatic rings are condensed with bicyclo[2.2.2]octane. Specific examples of the condensed ring-type group as R¹⁰¹ include those represented by General Formulae (r-br-1) and (r-br-2). In the formulae, * represents a bond that is bonded to Y¹⁰¹ in General Formula (b-1).

Examples of the substituent which the condensed ring-type group as R¹⁰¹ may have include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxy group, a carbonyl group, a nitro group, an aromatic hydrocarbon group, and an alicyclic hydrocarbon group.

Examples of the alkyl group, the alkoxy group, the halogen atom, and the halogenated alkyl group, as the substituent of the condensed ring-type group, include the same groups as those described as the substituent of the cyclic group as R¹⁰¹.

Examples of the aromatic hydrocarbon group as the substituent of the condensed ring-type group include a group in which one hydrogen atom has been removed from the above-described aromatic ring (an aryl group, for example, a phenyl group and a naphthyl group), a group in which one hydrogen atom in the aromatic ring has been substituted with an alkylene group (for example, arylalkyl groups such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, 1-naphthylethyl group, and a 2-naphthylethyl group), and heterocyclic groups respectively represented by General Formulae (r-hr-1) to (r-hr-6).

Examples of the alicyclic hydrocarbon group as the substituent of the condensed ring-type group include a group in which one hydrogen atom has been removed from monocycloalkanes such as cyclopentane and cyclohexane; a group in which one hydrogen atom has been removed from polycycloalkanes such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane; lactone-containing cyclic groups respectively represented by General Formulae (a2-r-1) to (a2-r-7); —SO₂— containing cyclic groups respectively represented by General Formulae (a5-r-1) to (a5-r-4); and heterocyclic groups respectively represented by General Formulae (r-hr-7) to (r-hr-16).

Chain alkyl group which may have substituent:

The chain alkyl group as R¹⁰¹ may be linear or branched.

The linear alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and most preferably 1 to 10 carbon atoms.

The branched alkyl group preferably has 3 to 20 carbon atoms, more preferably 3 to 15, and most preferably 3 to 10. Specific examples thereof include a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, and a 4-methylpentyl group.

Chain alkenyl group which may have substituent:

The chain alkenyl group as R¹⁰¹ may be linear or branched, and preferably has 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms, still more preferably 2 to 4 carbon atoms, and particularly preferably 3 carbon atoms. Examples of the linear alkenyl group include a vinyl group, a 1-propenyl group, a 2-propenyl group (an allyl group), and a butynyl group. Examples of the branched alkenyl group include a 1-methylvinyl group, a 1-methylpropenyl group, and a 2-methylpropenyl group.

Among the above, the chain alkenyl group is preferably a linear alkenyl group, more preferably a vinyl group or a propenyl group, and particularly preferably a vinyl group.

Examples of the substituent in the chain alkyl group or alkenyl group as R¹⁰¹ include an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxy group, a carbonyl group, a nitro group, an amino group, and a cyclic group as R¹⁰¹

Among the above, R¹⁰¹ is preferably a cyclic group which may have a substituent and more preferably a cyclic hydrocarbon group which may have a substituent. More specific examples of the cyclic hydrocarbon group preferably include a group in which one or more hydrogen atoms have been removed from a phenyl group, a naphthyl group, or a polycycloalkane; lactone-containing cyclic groups respectively represented by General Formulae (a2-r-1) to (a2-r-7); and —SO₂-containing cyclic groups respectively represented by General Formulae (a5-r-1) to (a5-r-4).

In General Formula (b-1), Y¹⁰ represents a single bond or a divalent linking group containing an oxygen atom.

In a case where Y¹⁰¹ represents a divalent linking group containing an oxygen atom, Y¹⁰¹ may contain an atom other than an oxygen atom. Examples of atoms other than an oxygen atom include a carbon atom, a hydrogen atom, a sulfur atom, and a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom include non-hydrocarbon-based oxygen atom-containing linking groups such as an oxygen atom (an ether bond; —O—), an ester bond (—C(═O)—O—), an oxycarbonyl group (—O—C(═O)—), an amide bond (—C(═O)—NH—), a carbonyl group (—C(═O)—), or a carbonate bond (—O—C(═O)—O—); and combinations of the above-described non-hydrocarbon-based oxygen atom-containing linking groups with an alkylene group. Furthermore, a sulfonyl group (—SO₂—) may be linked to the combination. Examples of divalent linking groups containing an oxygen atom include linking groups respectively represented by General Formulae (y-al-1) to (y-al-7) shown below.

[In the formulae, V′¹⁰¹ represents a single bond or an alkylene group having 1 to 5 carbon atoms, and V′¹⁰² represents a divalent saturated hydrocarbon group having 1 to 30 carbon atoms.]

The divalent saturated hydrocarbon group as V′¹⁰² is preferably an alkylene group having 1 to 30 carbon atoms, more preferably an alkylene group having 1 to 10 carbon atoms, and still more preferably an alkylene group having 1 to 5 carbon atoms.

The alkylene group as V′¹⁰¹ and V′¹⁰² may be a linear alkylene group or a branched alkylene group, and a linear alkylene group is preferable.

Specific examples of the alkylene group as V′¹⁰¹ and V′¹⁰² include a methylene group [—CH₂—]; an alkylmethylene group such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, or —C(CH₂CH₃)₂—; an ethylene group [—CH₂CH₂—]; an alkylethylene group such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, or —CH(CH₂CH₃)CH₂—; a trimethylene group (n-propylene group) [—CH₂CH₂CH₂—]; an alkyltrimethylene group such as —CH(CH₃)CH₂CH₂— or —CH₂CH(CH₃)CH₂—; a tetramethylene group [—CH₂CH₂CH₂CH₂—]; an alkyltetramethylene group such as —CH(CH₃)CH₂CH₂CH₂—, or —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylene group [—CH₂CH₂CH₂CH₂CH₂—].

Further, a part of a methylene group in the alkylene group as V′¹⁰¹ and V′¹⁰² may be substituted with a divalent aliphatic cyclic group having 5 to 10 carbon atoms. The aliphatic cyclic group is preferably a divalent group in which one hydrogen atom has been removed from the cyclic aliphatic hydrocarbon group (a monocyclic aliphatic hydrocarbon group or a polycyclic aliphatic hydrocarbon group) as Ra′³ in General Formula (a1-r-1), and a cyclohexylene group, a 1,5-adamantylene group, or a 2,6-adamantylene group is more preferable.

Y¹⁰¹ preferably represents a divalent linking group containing an ester bond or a divalent linking group containing an ether bond and more preferably linking groups respectively represented by General Formulae (y-al-1) to (y-al-5).

In General Formula (b-1), V¹⁰¹ represents a single bond, an alkylene group, or a fluorinated alkylene group. The alkylene group and the fluorinated alkylene group as V¹⁰¹ preferably have 1 to 4 carbon atoms. Examples of the fluorinated alkylene group as V¹⁰¹ include a group in which part or all of hydrogen atoms in the alkylene group as V¹⁰¹ have been substituted with a fluorine atom. Among them, V¹⁰¹ is preferably a single bond or a fluorinated alkylene group having 1 to 4 carbon atoms.

In General Formula (b-1), R¹⁰² represents a fluorine atom or a fluorinated alkyl group having 1 to 5 carbon atoms. R¹⁰² preferably represents a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms and more preferably a fluorine atom.

Specific examples of the anion moiety represented by General Formula (b-1) include a fluorinated alkylsulfonate anions such as a trifluoromethanesulfonate anion and a perfluorobutanesulfonate anion in a case where Y¹⁰¹ represents a single bond; and anions respectively represented by General Formulae (an-1) to (an-3) shown below in a case where Y¹⁰¹ represents a divalent linking group containing an oxygen atom.

[In the formula, R″¹⁰¹ represents an aliphatic cyclic group which may have a substituent, monovalent heterocyclic groups respectively represented by Chemical Formulae (r-hr-1) to (r-hr-6), a condensed ring-type group represented by General Formula (r-br-1) or (r-br-2), and a chain alkyl group which may have a substituent. R″¹⁰² is an aliphatic cyclic group which may have a substituent, a condensed ring-type group represented by General Formula (r-br-1) or (r-br-2), lactone-containing cyclic groups respectively represented by General Formulae (a2-r-1), (a2-r-3) to (a2-r-7), or —SO₂-containing cyclic groups respectively represented by General Formulae (a5-r-1) to (a5-r-4). R″¹⁰³ represents an aromatic cyclic group which may have a substituent, an aliphatic cyclic group which may have a substituent, or a chain alkenyl group which may have a substituent. V″¹⁰¹ represents a single bond, an alkylene group having 1 to 4 carbon atoms, or a fluorinated alkylene group having 1 to 4 carbon atoms. R¹⁰² represents a fluorine atom or a fluorinated alkyl group having 1 to 5 carbon atoms. v″s each independently represent an integer in a range of 0 to 3, q″s each independently represent an integer in a range of 0 to 20, and n″ represents 0 or 1.]

The aliphatic cyclic group as R″¹⁰¹, R″¹⁰², and R″¹⁰³, which may have a substituent, is preferably the group exemplified as the cyclic aliphatic hydrocarbon group as R¹⁰¹ in General Formula (b-1). Examples of the substituent include the same group as the substituent with which the cyclic aliphatic hydrocarbon group as R¹⁰¹ in General Formula (b-1) may be substituted.

The aromatic cyclic group which may have a substituent, as R″¹⁰³ is preferably the group exemplified as the aromatic hydrocarbon group for the cyclic hydrocarbon group as R¹⁰¹ in General Formula (b-1). Examples of the substituent include the same groups as the substituent with which the aromatic hydrocarbon group as R¹⁰¹ in General Formula (b-1) may be substituted.

The chain alkyl group as R″¹⁰¹, which may have a substituent, is preferably the group exemplified as the chain alkyl group as R¹⁰¹ in General Formula (b-1).

The chain alkenyl group as R″¹⁰³, which may have a substituent, is preferably the group exemplified as the chain alkenyl group as R¹⁰¹ in General Formula (b-1).

Anion in Component (b-2)

in General Formula (b-2), R¹⁰⁴ and R¹⁰⁵ each independently represent a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent, and has the same definition as that for R¹⁰¹ in General Formula (b-1). R¹⁰⁴ and R¹⁰⁵ may be bonded to each other to form a ring.

R¹⁰⁴ and R¹⁰⁵ are preferably a chain alkyl group which may have a substituent and more preferably a linear or branched alkyl group or a linear or branched fluorinated alkyl group.

The chain alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 7 carbon atoms, and still more preferably 1 to 3 carbon atoms. It is preferable that the number of carbon atoms in the chain alkyl group as R¹⁰⁴ and R¹⁰⁵ be small since the solubility in a solvent for a resist is also excellent in this range of the number of carbon atoms. Further, in the chain alkyl group as R¹⁰⁴ and R¹⁰⁵, it is preferable that the number of hydrogen atoms substituted with a fluorine atom be large since the acid strength increases and the transparency to high energy radiation of 250 nm or less or electron beams is improved. The proportion of fluorine atoms in the chain alkyl group, that is, the fluorination ratio is preferably in a range of 70% to 100% and more preferably in a range of 90% to 100%, and it is most preferable that the chain alkyl group be a perfluoroalkyl group in which all hydrogen atoms be substituted with a fluorine atom.

in General Formula (b-2), V¹⁰² and V¹⁰³ each independently represent a single bond, an alkylene group, or a fluorinated alkylene group, and has the same definition as that for V¹⁰¹ in General Formula (b-1).

In General Formula (b-2), L¹⁰¹ and L¹⁰² each independently represent a single bond or an oxygen atom.

Anion in Component (b-3)

in General Formula (b-3), R¹⁰⁶ to R¹⁰⁸ each independently represents a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent, and has the same definition as that for R¹⁰¹ in General Formula (b-1) In General Formula (b-3), L¹⁰³ to L¹⁰⁵ each independently represents a single bond, —CO—, or —SO₂—.

Examples of the onium salt-based acid generator in the component (B1) include a compound represented by General Formula (b-0) (hereinafter, also referred to as a “component (b-0)”).

R¹⁰⁰—SO₃ ⁻

(M′^(m+))_(1/m)  (b-0)

[In General Formula, R¹⁰⁰ represents a halogenated alkyl group which may have a substituent, a cyclic group which may have a substituent, or an alkenyl group which may have a substituent. m represents an integer of 1 or greater, and M′^(m+) represents an m-valent onium cation.]

Anion in Component (b-0)

[In General Formula (b-0), R¹⁰⁰ represents a halogenated alkyl group which may have a substituent, a cyclic group which may have a substituent, or an alkenyl group which may have a substituent.

Examples of the halogenated alkyl group as R¹⁰⁰ include a group in which part or all of hydrogen atoms in the linear, branched, or cyclic alkyl group have been substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and, an iodine atom, and a fluorine atom is preferable.

In a case of being a linear or branched alkyl group, the alkyl group in the halogenated alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, particularly preferably 1 to 4 carbon atoms; and in a case of being a cyclic alkyl group, the alkyl group preferably has 4 to 15 carbon atoms, more preferably 4 to 10 carbon atoms, and particularly preferably 6 to 10 carbon atoms.

In the halogenated alkyl group, the proportion of the number of halogen atoms (halogenation rate (%)) to the total number of halogen atoms and hydrogen atoms contained in the halogenated alkyl group is preferably 10% to 100%, more preferably 50% to 100%, and most preferably 100%. The higher the halogenation rate, the stronger the acid strength, which is preferable.

The cyclic group as R¹⁰⁰ is preferably a cyclic hydrocarbon group, and the cyclic hydrocarbon group may be an aromatic hydrocarbon group or an aliphatic hydrocarbon group; however, it is preferably an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be saturated or unsaturated. In general, it is preferable that the aliphatic hydrocarbon group be saturated.

The cyclic aliphatic hydrocarbon group as R¹⁰⁰ is preferably a group in which one or more hydrogen atoms have been removed from adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane, or the like; or a group in which one or more hydrogen atoms have been removed from camphor or the like. Among these, a group in which one or more hydrogen atoms have been removed from camphor is more preferable.

The alkenyl group as R¹⁰⁰ preferably an alkenyl group having 2 to 10 carbon atoms.

In regard to R¹⁰⁰, “may have a substituent” means that part or all of hydrogen atoms in the halogenated alkyl group, the cyclic group, or the alkenyl group may be substituted with a substituent (an atom other than the hydrogen atom or a group). The number of substituents in R¹⁰⁰ may be one or two or more.

Examples of the substituent in R¹⁰⁰ include a halogen atom, a hetero atom, and an alkyl group.

Examples of the halogen atom and the alkyl group include the same substituents as those exemplified as the halogen atom and the alkyl group in the halogenated alkyl group as R¹⁰⁰.

Examples of the hetero atom include an oxygen atom, a nitrogen atom, and a sulfur atom.

Specific examples of the anion moiety “R¹⁰⁰—SO₃—” of the compound represented by General Formula (b-0) include trifluoromethanesulfonate, heptafluoropropanesulfonate, nonafluorobutanesulfonate, 1-adamantanesulfonate, 2-norbornanesulfonate, d-camphor-10-sulfonate, benzenesulfonate, perfluorobenzenesulfonate, and p-toluenesulfonate.

{Cation Moiety}

In General Formula (b-1), General Formula (b-2), General Formula (b-3), and in General Formula (b-0), M′^(m+) represents an m-valent onium cation. Among these, a sulfonium cation and an iodonium cation are preferable.

m represents an integer of 1 or greater.

Preferred examples of the cation moiety ((M′^(m+))_(1/m)) include organic cations each represented by General Formulae (ca-1) to (ca-5).

[In the formulae, R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² each independently represent an aryl group which may have a substituent, an alkyl group which may have a substituent, or an alkenyl group which may have a substituent. R²⁰¹ to R²⁰³, R²⁰⁶ and R²⁰⁷, or R²¹¹ and R²¹ may be bonded to each other to form a ring together with the sulfur atom in the formula. R²⁰⁸ and R²⁰⁹ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R²¹⁰ represents an aryl group which may have a substituent, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or a —SO₂-containing cyclic group which may have a substituent. L²⁰¹ represents —C(═O)— or —C(═O)—O—. Y²⁰¹s each independently represent an arylene group, an alkylene group, or an alkenylene group. x represents 1 or 2. W²⁰¹ represents an (x+1)-valent linking group.]

In General Formulae (ca-1) to (ca-5), examples of the aryl group as R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² include an unsubstituted aryl group having 6 to 20 carbon atoms, and a phenyl group or a naphthyl group is preferable.

The alkyl group as R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² is preferably a chain or cyclic alkyl group preferably has 1 to 30 carbon atoms.

The alkenyl group as R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² preferably has 2 to 10 carbon atoms.

Examples of the substituent which may be included in R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹² include an alkyl group, a halogen atom, a halogenated alkyl group, a carbonyl group, a cyano group, an amino group, an aryl group, and groups respectively represented by General Formulae (ca-r-1) to (ca-r-7) shown above.

[In the formulae, R′²⁰¹s each independently represent a hydrogen atom, a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent.]

Cyclic group which may have substituent:

The cyclic group is preferably a cyclic hydrocarbon group, and the cyclic hydrocarbon group may be an aromatic hydrocarbon group or an aliphatic hydrocarbon group. The aliphatic hydrocarbon group indicates a hydrocarbon group that has no aromaticity. The aliphatic hydrocarbon group may be saturated or unsaturated. In general, it is preferable that the aliphatic hydrocarbon group be saturated.

The aromatic hydrocarbon group as R′²⁰¹ is a hydrocarbon group having an aromatic ring. The aromatic hydrocarbon group preferably has 3 to 30 carbon atoms, more preferably 5 to 30 carbon atoms, still more preferably 5 to 20 carbon atoms, particularly preferably 6 to 15 carbon atoms, and most preferably 6 to 10 carbon atoms. Here, the number of carbon atoms in a substituent is not included in the number of carbon atoms.

Specific examples of the aromatic ring which the aromatic hydrocarbon group has as R′²⁰¹ include benzene, fluorene, naphthalene, anthracene, phenanthrene, biphenyl, or an aromatic heterocyclic ring in which some carbon atoms constituting any of these aromatic rings have been substituted with a hetero atom. Examples of the hetero atom in the aromatic heterocyclic rings include an oxygen atom, a sulfur atom, and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group as R′²⁰¹ include a group in which one hydrogen atom has been removed from the above-described aromatic ring (an aryl group such as a phenyl group or a naphthyl group) and a group in which one hydrogen atom in the aromatic ring has been substituted with an alkylene group (an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, 1-naphthylethyl group, or a 2-naphthylethyl group). The alkylene group (an alkyl chain in the arylalkyl group) preferably has 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms, and particularly preferably 1 carbon atom.

Examples of the cyclic aliphatic hydrocarbon group as R′²⁰¹ include aliphatic hydrocarbon groups containing a ring in the structure thereof.

Examples of the aliphatic hydrocarbon group containing a ring in the structure thereof include an alicyclic hydrocarbon group (a group in which one hydrogen atom has been removed from an aliphatic hydrocarbon ring), a group in which the alicyclic hydrocarbon group is bonded to the terminal of a linear or branched aliphatic hydrocarbon group, and a group in which the alicyclic hydrocarbon group is interposed in a linear or branched aliphatic hydrocarbon group.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms and more preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be a polycyclic group or a monocyclic group. The monocyclic alicyclic hydrocarbon group is preferably a group in which one or more hydrogen atoms have been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group in which one or more hydrogen atoms have been removed from a polycycloalkane, and the polycycloalkane preferably has 7 to 30 carbon atoms. Among them, the polycycloalkanes is preferably a polycycloalkane having a bridged ring-based polycyclic skeleton, such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane; or a polycycloalkane having a condensed ring-based polycyclic skeleton, such as a cyclic group having a steroid skeleton.

Among them, the cyclic aliphatic hydrocarbon group as R′²⁰¹ is preferably a group in which one or more hydrogen atoms have been removed from a monocycloalkane or a polycycloalkane, more preferably a group in which one hydrogen atom has been removed from a polycycloalkane, particularly preferably an adamantyl group or a norbornyl group, and most preferably an adamantyl group.

The linear or branched aliphatic hydrocarbon group which may be bonded to the alicyclic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and particularly preferably 1 to 3 carbon atoms.

The linear aliphatic hydrocarbon group is preferably a linear alkylene group, and specific examples thereof include a methylene group [—CH₂—], an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], a tetramethylene group [—(CH₂)₄—], and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group is preferably a branched alkylene group, and specific examples thereof include alkylalkylene groups, for example, alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—; alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; and alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and —CH₂CH(CH₃)CH₂CH₂—. The alkyl group in the alkylalkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

The cyclic hydrocarbon group as R′201 may contain a hetero atom such as a heterocyclic ring. Specific examples thereof include lactone-containing cyclic groups respectively represented by General Formulae (a2-r-1) to (a2-r-7), —SO₂-containing cyclic groups respectively represented by General Formulae (a5-r-1) to (a5-r-4), and other heterocyclic groups respectively represented by Chemical Formulae (r-hr-1) to (r-hr-16).

Examples of the substituent of the cyclic group as R′²⁰¹ include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxy group, a carbonyl group, and a nitro group.

The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group is most preferable.

The alkoxy group as the substituent is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, or a tert-butoxy group, and most preferably a methoxy group or an ethoxy group.

The halogen atom as the substituent is preferably a fluorine atom.

Examples of the above-described halogenated alkyl group as the substituent include a group in which part or all of hydrogen atoms in an alkyl group having 1 to 5 carbon atoms such as a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group have been substituted with the above-described halogen atom. The carbonyl group as a substituent is a group that is substituted for a methylene group (—CH₂—) constituting the cyclic hydrocarbon group.

Chain alkyl group which may have substituent:

The chain alkyl group as R′²⁰¹ may be linear or branched.

The linear alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and most preferably 1 to 10 carbon atoms.

The branched alkyl group preferably has 3 to 20 carbon atoms, more preferably 3 to 15 carbon atoms, and most preferably 3 to 10 carbon atoms. Specific examples thereof include a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, and a 4-methylpentyl group.

Chain alkenyl group which may have substituent:

Such a chain alkenyl group as R′²⁰¹ may be linear or branched, preferably has 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms, still more preferably 2 to 4 carbon atoms, and particularly preferably 3 carbon atoms. Examples of the linear alkenyl group include a vinyl group, a 1-propenyl group, a 2-propenyl group (an allyl group), and a butynyl group. Examples of the branched alkenyl group include a 1-methylvinyl group, a 1-methylpropenyl group, and a 2-methylpropenyl group.

Among the above, the chain alkenyl group is preferably a linear alkenyl group, more preferably a vinyl group or a propenyl group, and particularly preferably a vinyl group.

Examples of the substituent in the chain alkyl group or alkenyl group as R′²⁰¹, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxy group, a carbonyl group, a nitro group, an amino group, a cyclic group as R′²⁰¹ or the like may be used.

As the cyclic group which may have a substituent, the chain alkyl group which may have a substituent, or the chain alkenyl group which may have a substituent, as R²⁰¹, a group that is the same as the acid-dissociable group represented by above-described General Formula (a1-r-2) can be mentioned as the cyclic group which may have a substituent or the chain alkyl group which may have a substituent, in addition to the groups described above.

Among them, R′²⁰¹ is preferably a cyclic group which may have a substituent and more preferably a cyclic hydrocarbon group which may have a substituent. More specific examples thereof preferably include a group in which one or more hydrogen atoms have been removed from a phenyl group, a naphthyl group, or a polycycloalkane; lactone-containing cyclic groups respectively represented by General Formulae (a2-r-1) to (a2-r-7); and —SO₂-containing cyclic groups respectively represented by General Formulae (a5-r-1) to (a5-r-4).

In General Formulae (ca-1) to (ca-5), in a case where R²⁰¹ to R²⁰³, R²⁰⁶ and R²⁰⁷, or R²¹¹ and R²¹² are bonded to each other to form a ring with a sulfur atom in the formula, these groups may be bonded to each other via a hetero atom such as a sulfur atom, an oxygen atom or a nitrogen atom, or a functional group such as a carbonyl group, —SO—, —SO₂—, —SO₃—, —COO—, —CONH—, or —N(R_(N))— (here, R_(N) represents an alkyl group having 1 to 5 carbon atoms). As the ring to be formed, a ring containing the sulfur atom in the formula in the ring skeleton thereof is preferably a 3- to 10-membered ring and particularly preferably a 5- to 7-membered ring including the sulfur atom. Specific examples of the ring to be formed include a thiophene ring, a thiazole ring, a benzothiophene ring, a dibenzothiophene ring, a 9H-thioxanthene ring, a thioxanthone ring, a thianthrene ring, a phenoxathiin ring, a tetrahydrothiophenium ring, and a tetrahydrothiopyranium ring.

R²⁰⁸ and R²⁰⁹ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms and are preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. In a case where R²⁰⁸ and R²⁰⁹ each independently represent an alkyl group, R²⁰⁸ and R²⁰⁹ may be bonded to each other to form a ring.

R²¹⁰ represents an aryl group which may have a substituent, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or a —SO₂-containing cyclic group which may have a substituent.

Examples of the aryl group as R²¹⁰ include an unsubstituted aryl group having 6 to 20 carbon atoms, and a phenyl group or a naphthyl group is preferable. The alkyl group as R²¹⁰, a chain or cyclic alkyl group having 1 to 30 carbon atoms is preferable.

The alkenyl group as R²¹⁰ preferably has 2 to 10 carbon atoms. The —SO₂-containing cyclic group which may have a substituent, as R²¹⁰, is preferably a “—SO₂-containing polycyclic group”, and more preferably a group represented by General Formula (a5-r-1).

Y²⁰¹s each independently represent an arylene group, an alkylene group, or an alkenylene group.

Examples of the arylene group as Y²⁰¹ include groups in which one hydrogen atom has been removed from an aryl group mentioned as the aromatic hydrocarbon group represented by R¹⁰¹ in General Formula (b-1) described above.

Examples of the alkylene group and alkenylene group as Y²⁰¹ include groups in which one hydrogen atom has been removed from the chain alkyl group or the chain alkenyl group as R¹⁰¹ in General Formula (b-1) described above.

In General Formulae (ca-4) and (ca-5), x represents 1 or 2.

W²⁰¹ represents an (x+1)-valent linking group, that is, a divalent or trivalent linking group.

The divalent linking group as W²⁰¹ is preferably a divalent hydrocarbon group which may have a substituent, and examples thereof include the divalent hydrocarbon group, which may have a substituent, exemplified in the description for “polymerizable group-containing group” as W¹ in General Formula (a01-1) described above. The divalent linking group as W²⁰¹ may be linear, branched, or cyclic and is preferably cyclic. Among them, an arylene group having two carbonyl groups, each bonded to both terminals thereof is preferable. Examples of the arylene group include a phenylene group and a naphthylene group, and a phenylene group is particularly preferable. Examples of the trivalent linking group as W²⁰¹ include a group in which one hydrogen atom has been removed from the above-described divalent linking group as W²⁰¹ and a group in which the divalent linking group has been bonded to another divalent linking group. The trivalent linking group as W²⁰¹ is preferably a group in which two carbonyl groups are bonded to an arylene group.

Suitable examples of the cation represented by General Formula (ca-1) are as follows.

[In the formulae, g1, g2, and g3 represent the numbers of repetitions, g1 is an integer in a range of 1 to 5, g2 is an integer in a range of 0 to 20, and g3 is an integer in a range of 0 to 20.]

[In the formula, R″²⁰¹ represents a hydrogen atom or a substituent, and examples of the substituent include the same substituent as that exemplified as the substituent which R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹² may have.]

Specific examples of the suitable cation represented by General Formula (ca-2) include a diphenyliodonium cation and a bis(4-tert-butylphenyl)iodonium cation.

Specific examples of the suitable cation represented by General Formula (ca-3) include cations respectively represented by General Formulae (ca-3-1) to (ca-3-6) shown below.

Specific examples of the suitable cation represented by General Formula (ca-4) include cations respectively represented by General Formulae (ca-4-1) and (ca-4-2) shown below.

Specific examples of the suitable cation represented by General Formula (ca-5) include cations respectively represented by General Formulae (ca-5-1) to (ca-5-3) shown below.

In the resist composition according to the present embodiment, the component (B1) may be used alone or in a combination of two or more kinds thereof.

Among the above, the anion moiety of the component (B1) is preferably an anion of the component (b-1). Among these, an anion represented by any one of General Formulae (an-1) to (an-3) is more preferable, an anion represented by any one of General Formula (an-1) or (an-2) is still more preferable.

In addition, among the above, the cation moiety of the component (B1) is preferably a cation represented by General Formula (ca-1).

The content of the component (B1) in the resist composition according to the present embodiment is preferably in a range of 5 to 50 parts by mass, more preferably in a range of 5 to 45 parts by mass, and still more preferably in a range of 10 to 40 parts by mass, with respect to 100 parts by mass of the component (A1).

In a case where the content of the component (B1) is equal to or greater than the lower limit of the preferred range described above, high sensitivity is easily achieved, and excellent lithography characteristics are easily improved. On the other hand, in a case where the content of the component (B1) is equal to or lower than the upper limit of the preferred range described above, a uniform solution is easily obtained, and the storage stability of the resist composition is improved in a case where being dissolved in an organic solvent.

<Optional Component>

The resist composition according to the present embodiment may further contain other components (an optional component) in addition to the component (A) and the component (B) described above. Examples of the optional component include a component (D), a component (E), a component (F), and a component (S).

<<Component (D)>>

The resist composition according to the present embodiment may further contain, in addition to the components (A) and (B), a base component (component (D)) that traps (that is, controls the diffusion of an acid) an acid generated from the component (B) upon exposure. The component (D) acts as a quencher (an acid diffusion-controlling agent) which traps the acid generated in the resist composition upon exposure.

Examples of the component (D) include a photodecomposable base (D1) having an acid diffusion controllability (hereinafter, referred to as a “component (D1)”) which is lost by the decomposition upon exposure and a nitrogen-containing organic compound (D2) (hereinafter, referred to as a “component (D2)”) which does not correspond to the component (D1)

In Regard to Component (D1)

In a case where a resist composition containing the component (D1) is obtained, the contrast between the exposed portion and the unexposed portion of the resist film can be further improved at the time of the formation of a resist pattern. The component (D1) is not particularly limited as long as it is decomposed upon exposure and loses the acid diffusion controllability. The component (D1) is preferably one or more compounds selected from the group consisting of a compound represented by General Formula (d1-1) (hereinafter, referred to as a “component (d1-1)”), a compound represented by General Formula (d1-2) (hereinafter, referred to as a “component (d1-2)”), and a compound represented by General Formula (d1-3) (hereinafter, referred to as a “component (d1-3)”).

At the exposed portion of the resist film, the components (d1-1) to (d1-3) are decomposed and then lose the acid diffusion controllability (basicity), and thus the components (d1-1) to (d1-3) cannot act as a quencher, whereas the components (d1-1) to (d1-3) act as a quencher at the unexposed portion of the resist film.

[In the formulae, Rd¹ to Rd⁴ represent cyclic groups which may have a substituent, chain alkyl groups which may have a substituent, or chain alkenyl groups which may have a substituent. Here, the carbon atom adjacent to the S atom as Rd² in General Formula (d1-2) has no fluorine atom bonded thereto. Yd¹ represents a single bond or a divalent linking group. m represents an integer of 1 or greater, and M^(m+)s each independently represent an m-valent organic cation.]

{Component (d1-1)}

Anion Moiety

In General Formula (d1-1), Rd¹ represents a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent, which is the same as that described above as R′201

Among these, Rd¹ is preferably an aromatic hydrocarbon group which may have a substituent, an aliphatic cyclic group which may have a substituent, or a chain alkyl group which may have a substituent. Examples of the substituent which these groups may have include a hydroxy group, an oxo group, an alkyl group, an aryl group, a fluorine atom, a fluorinated alkyl group, lactone-containing cyclic groups respectively represented by any of General Formulae (a2-r-1) to (a2-r-7) described above, an ether bond, an ester bond, and a combination thereof. In a case where an ether bond or an ester bond is included as a substituent, the substituent may be bonded via an alkylene group, and linking groups respectively represented by any of Formulae (y-al-1) to (y-al-5) are preferable as the substituent.

Suitable examples of the aromatic hydrocarbon group include a phenyl group, a naphthyl group, and a polycyclic structure (a polycyclic structure including a bicyclooctane skeleton and a ring structure other than the bicyclooctane skeleton) including a bicyclooctane skeleton.

The aliphatic cyclic group is preferably a group in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane.

The chain alkyl group preferably has 1 to 10 carbon atoms, and specific examples thereof include a linear alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, or a decyl group, and a branched alkyl group such as a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, or a 4-methylpentyl group.

In a case where the chain alkyl group is a fluorinated alkyl group having a fluorine atom or a fluorinated alkyl group as a substituent, the fluorinated alkyl group preferably has 1 to 11 carbon atoms, more preferably 1 to 8 carbon atoms, and still more preferably 1 to 4 carbon atoms. The fluorinated alkyl group may contain an atom other than a fluorine atom. Examples of the atom other than a fluorine atom include an oxygen atom, a sulfur atom, and a nitrogen atom.

Rd¹ is preferably a fluorinated alkyl group in which part or all of hydrogen atoms constituting a linear alkyl group have been substituted with a fluorine atom and particularly preferably a fluorinated alkyl group in which all of the hydrogen atoms constituting a linear alkyl group have been substituted with a fluorine atom (a linear perfluoroalkyl group).

Specific examples of the preferred anion moiety for the component (d1-1) are shown below.

In General Formula (d1-1), M⁺ represents an m-valent organic cation. Suitable examples of the organic cation of M^(m+) include the same cations as those respectively represented by General Formulae (ca-1) to (ca-5), and the cation represented by General Formula (ca-1) is preferable, and cations respectively represented by General Formulae (ca-1-1) to (ca-1-117) are more preferable.

The component (d1-1) may be used alone or in a combination of two or more kinds thereof

{Component (d1-2)}

Anion Moiety

In General Formula (d1-2), Rd² represents a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent, and examples thereof include the same group as that described above as R′²⁰¹.

Here, the carbon atom adjacent to the S atom in Rd² has no fluorine atom bonded thereto (the carbon atom adjacent to the S atom in Rd² is not substituted with a fluorine atom). As a result, the anion of the component (d1-2) becomes an appropriately weak acid anion, thereby improving the quenching ability of the component (D).

Rd² is preferably a chain alkyl group which may have a substituent or an aliphatic cyclic group which may have a substituent. The chain alkyl group preferably has 1 to 10 carbon atoms and more preferably 3 to 10 carbon atoms. The aliphatic cyclic group is more preferably a group (which may have a substituent) in which one or more hydrogen atoms have been removed from adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane, or the like; and a group in which one or more hydrogen atoms have been removed from camphor or the like.

The hydrocarbon group as Rd² may have a substituent. Examples of the substituent include the same substituent as that which the hydrocarbon group (an aromatic hydrocarbon group, an aliphatic cyclic group, or a chain alkyl group) as Rd¹ In General Formula (d1-1) may have.

Specific examples of the preferred anion moiety for the component (d1-2) are shown below.

Cation Moiety

In General Formula (d1-2), M^(m+) represents an m-valent organic cation and has the same definition as that for M^(m+) In General Formula (d1-1).

The component (d1-2) may be used alone or in a combination of two or more kinds thereof.

{Component (d1-3)}

Anion Moiety

In General Formula (d1-3), Rd³ represents a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent, examples thereof include the same group as that described above as R′²⁰¹, and a cyclic group containing a fluorine atom, a chain alkyl group, or a chain alkenyl group is preferable. Among them, a fluorinated alkyl group is preferable, and the same fluorinated alkyl group as that described above as Rd¹ is more preferable.

In General Formula (d1-3), Rd⁴ represents a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent, and examples thereof include the same group as that described above as R′²⁰¹.

Among them, an alkyl group which may have a substituent, an alkoxy group which may have a substituent, an alkenyl group which may have a substituent, or a cyclic group which may have a substituent is preferable.

The alkyl group as Rd⁴ is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. A part of hydrogen atoms in the alkyl group as Rd⁴ may be substituted with a hydroxy group, a cyano group, or the like.

The alkoxy group as Rd⁴ is preferably an alkoxy group having 1 to 5 carbon atoms, and specific examples of the alkoxy group having 1 to 5 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, and a tert-butoxy group. Among them, a methoxy group and an ethoxy group are preferable.

Examples of the alkenyl group as Rd⁴ include the same group as the alkenyl group described above as R′²⁰¹, and a vinyl group, a propenyl group (an allyl group), a 1-methylpropenyl group, or a 2-methylpropenyl group is preferable. These groups may further have an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms as a substituent.

Examples of the cyclic group as Rd⁴ include the same group as the cyclic group described above as R′²⁰¹ and an alicyclic group in which one or more hydrogen atoms have been removed from a cycloalkane such as cyclopentane, cyclohexane, adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane, or an aromatic group such as a phenyl group or a naphthyl group is preferable. In a case where Rd⁴ represents an alicyclic group, the resist composition can be satisfactorily dissolved in an organic solvent, thereby improving lithography characteristics. In a case where Rd⁴ is an aromatic group, the resist composition is excellent in light absorption efficiency and thus has good sensitivity and lithography characteristics in lithography using EUV or the like as a light source for exposure.

In General Formula (d1-3), Yd¹ represents a single bond or a divalent linking group.

The divalent linking group as Yd¹ is not particularly limited, and examples thereof include a divalent hydrocarbon group (an aliphatic hydrocarbon group or an aromatic hydrocarbon group) which may have a substituent and a divalent linking group containing a hetero atom. Examples thereof include the same groups as the divalent hydrocarbon group which may have a substituent and the divalent linking group containing a hetero atom, which are respectively exemplified in the description for “polymerizable group-containing group” as W¹ in General Formula (a01-1) described above.

Yd¹ is preferably a carbonyl group, an ester bond, an amide bond, an alkylene group, or a combination thereof. The alkylene group is preferably a linear or branched alkylene group and more preferably a methylene group or an ethylene group.

Specific examples of the preferred anion moiety for the component (d1-3) are shown below.

Cation Moiety

In General Formula (d1-3), M^(m+) represents an m-valent organic cation and has the same definition as that for M^(m) In General Formula (d1-1).

The component (d1-3) may be used alone or in a combination of two or more kinds thereof.

As the component (D1), only one of the above-described components (d1-1) to (d1-3) or a combination of two or more kinds thereof may be used.

In a case where the resist composition contains the component (D1), the content of the component (D1) in the resist composition is preferably in a range of 0.5 to 20 parts by mass, more preferably in a range of 1 to 15 parts by mass, and still more preferably in a range of 2 to 10 parts by mass with respect to 100 parts by mass of the component (A1).

In a case where the content of the component (D1) is equal to or greater than the preferred lower limit, excellent lithography characteristics and an excellent resist pattern shape are easily obtained. On the other hand, in a case where the content of the component (D1) is equal to or lower than the upper limit, the sensitivity can be maintained satisfactorily and the throughput is also excellent.

Method of Producing Component (D1):

The methods of producing the components (d1-1) and (d1-2) are not particularly limited, and the components (d1-1) and (d1-2) can be produced by conventionally known methods.

Further, the method of producing the component (d1-3) is not particularly limited, and the component (d1-3) can be produced in the same manner as disclosed in United States Patent Application, Publication No. 2012-0149916.

In Regard to Component (D2)

The acid diffusion-controlling agent may contain a nitrogen-containing organic compound component (hereinafter, referred to as a “component (D2)”) which does not correspond to the above-mentioned component (D1).

The component (D2) is not particularly limited as long as it acts as an acid diffusion-controlling agent and does not correspond to the component (D1), and any conventionally known compound may be used. Among the above, aliphatic amines are preferable, and among the aliphatic amines, a secondary aliphatic amine or a tertiary aliphatic amine is more preferable.

An aliphatic amine is an amine having one or more aliphatic groups, and the aliphatic groups preferably have 1 to 12 carbon atoms.

Examples of these aliphatic amines include an amine in which at least one hydrogen atom of ammonia (NH₃) has been substituted with an alkyl group or hydroxyalkyl group having 12 or fewer carbon atoms (alkyl amines or alkyl alcohol amines) and a cyclic amine.

Specific examples of alkyl amines and alkyl alcohol amines include monoalkyl amines such as n-hexyl amine, n-heptyl amine, n-octyl amine, n-nonyl amine, and n-decyl amine; dialkyl amines such as diethyl amine, di-n-propyl amine, di-n-heptyl amine, di-n-octyl amine, and dicyclohexyl amine; trialkyl amines such as trimethyl amine, triethyl amine, tri-n-propyl amine, tri-n-butyl amine, tri-n-hexyl amine, tri-n-pentyl amine, tri-n-heptyl amine, tri-n-octyl amine, tri-n-nonyl amine, tri-n-decyl amine, and tri-n-dodecyl amine; and alkyl alcohol amines such as diethanol amine, triethanol amine, diisopropanol amine, triisopropanol amine, di-n-octanol amine, and tri-n-octanol amine. Among these, trialkyl amines of 5 to 10 carbon atoms are preferable, and tri-n-pentyl amine and tri-n-octyl amine are particularly preferable.

Examples of the cyclic amine include heterocyclic compounds containing a nitrogen atom as a hetero atom. The heterocyclic compound may be a monocyclic compound (aliphatic monocyclic amine), or a polycyclic compound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidine and piperazine. The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, and specific examples thereof include 1, 5-diazabicyclo[4.3.0]-5-nonene, 1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and 1,4-diazabicyclo[2.2.2]octane.

Examples of the other aliphatic amines include tris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine, tris{2-(2-methoxyethoxymethoxy)ethyl}amine, tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine, tris{2-(1-ethoxypropoxy)ethyl}amine, tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine, and triethanol amine triacetate; and morpholine compounds such as morpholine, 4-methylmorpholine, 4-(2-hydroxyethyl)morpholine, and 2-morpholinoethyl laurate, and morpholine compounds are preferable.

In addition, as the component (D2), an aromatic amine may be used.

Examples of aromatic amines include 4-dimethylaminopyridine, pyrrole, indole, pyrazole, imidazole, and derivatives thereof, tribenzyl amine, 2,6-diisopropylaniline, and N-tert-butoxycarbonylpyrrolidine.

The component (D2) may be used alone or in a combination of two or more kinds thereof. In a case where the resist composition contains the component (D2), the content of the component (D2) in the resist composition is typically used in a range of 0.01 to 5 parts by mass with respect to 100 parts by mass of the component (A1). In a case where the content is within the above range, the resist pattern shape, the post-exposure temporal stability, and the like are improved.

<<Component (E)>>

For the purpose of preventing any deterioration in sensitivity, and improving the resist pattern shape and the post-exposure temporal stability, the resist composition according to the present embodiment may contain at least one compound (E) (hereinafter referred to as a component (E)) selected from the group consisting of an organic carboxylic acid, and a phosphorus oxo acid and a derivative thereof.

Examples of suitable organic carboxylic acids include acetic acid, malonic acid, citric acid, malic acid, succinic acid, benzoic acid, and salicylic acid.

Examples of phosphorus oxo acid include phosphoric acid, phosphonic acid, and phosphinic acid.

Among these, phosphonic acid is particularly preferable.

Examples of phosphorus oxo acid derivatives include esters in which a hydrogen atom in the above-described oxo acids is substituted with a hydrocarbon group.

Examples of the hydrocarbon group include an alkyl group having 1 to 5 carbon atoms and an aryl group having 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esters such as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esters such as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonic acid, diphenyl phosphonate, and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid esters and phenylphosphinic acid.

In the resist composition according to the present embodiment, the component (E) may be used alone or in a combination of two or more kinds thereof.

In a case where the resist composition contains the component (E), the content of the component (E) is typically in a range of 0.01 to 5 parts by mass with respect to 100 parts by mass of the component (A1).

<<Component (F)>>

The resist composition according to the present embodiment may further include a fluorine additive component (hereinafter, referred to as a “component (F)”) in order to impart water repellency to the resist film or to improve lithography characteristics.

As the component (F), a fluorine-containing high-molecular-weight compound described in Japanese Unexamined Patent Application, First Publication No. 2010-002870, Japanese Unexamined Patent Application, First Publication No. 2010-032994, Japanese Unexamined Patent Application, First Publication No. 2010-277043, Japanese Unexamined Patent Application, First Publication No. 2011-13569, and Japanese Unexamined Patent Application, First Publication No. 2011-128226 can be mentioned.

Specific examples of the component (F) include polymers having a constitutional unit (f1) represented by General Formula (f1-1) shown below. This polymer is preferably a polymer (homopolymer) consisting of a constitutional unit (f1) represented by General Formula (f1-1) shown below; a copolymer of the constitutional unit (f1) and the constitutional unit (a1); and a copolymer of the constitutional unit (f1), a constitutional unit derived from acrylic acid or methacrylic acid, and the above-described constitutional unit (a1). The constitutional unit (a1) to be copolymerized with the constitutional unit (f1) is preferably a constitutional unit derived from 1-ethyl-1-cyclooctyl (meth)acrylate or a constitutional unit derived from 1-methyl-1-adamantyl (meth)acrylate.

[In the formula, R has the same definition as described above. Rf¹⁰² and Rf¹⁰³ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms, and Rf⁰² and Rf¹⁰³ may be the same as or different from each other. nf¹ represents an integer in a range of 0 to 5, and Rf¹⁰¹ represents an organic group containing a fluorine atom.]

In General Formula (f1-1), R bonded to the carbon atom at the α-position has the same definition as described above. R is preferably a hydrogen atom or a methyl group.

In General Formula (f1-1), examples of the halogen atom as Rf¹⁰² and Rf³ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferable. Examples of the alkyl group having 1 to 5 carbon atoms as Rf¹⁰² and Rf¹⁰³ include those described above as the alkyl group having 1 to 5 carbon atoms as R, and a methyl group or an ethyl group is preferable. Specific examples of the halogenated alkyl group having 1 to 5 carbon atoms as Rf¹⁰² and Rf¹⁰³ include groups in which part or all of hydrogen atoms of the above-described alkyl groups of 1 to 5 carbon atoms have been substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and, an iodine atom, and a fluorine atom is particularly preferable. Among them, Rf¹⁰² and Rf¹⁰³ are preferably a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms, and more preferably a hydrogen atom, a fluorine atom, a methyl group, or an ethyl group.

In General Formula (f1-1), nf¹ represents an integer in a range of 0 to 5, preferably an integer in a range of 0 to 3, and more preferably an integer of 1 or 2.

In General Formula (f1-1), Rf¹⁰¹ represents an organic group containing a fluorine atom and is preferably a hydrocarbon group containing a fluorine atom.

The hydrocarbon group containing a fluorine atom may be linear, branched, or cyclic, and preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and particularly preferably 1 to 10 carbon atoms.

In addition, in the hydrocarbon group containing a fluorine atom, 25% or more of the hydrogen atoms in the hydrocarbon group are preferably fluorinated, more preferably 50% or more are fluorinated, and particularly preferably 60% or more are fluorinated since the hydrophobicity of the resist film during dipping exposure increases.

Among them, Rf¹⁰¹ is more preferably a fluorinated hydrocarbon group having 1 to 6 carbon atoms, still more preferably a trifluoromethyl group, and particularly preferably —CH₂—CF₃, —CH₂—CF₂—CF₃, —CH(CF₃)₂, —CH₂—CH₂—CF₃, or —CH₂—CH₂—CF₂—CF₂—CF₂—CF₃.

The weight-average molecular weight (Mw) (based on the polystyrene-equivalent value determined by gel permeation chromatography) of the component (F) is preferably in a range of 1,000 to 50,000, more preferably in a range of 5,000 to 40,000, and most preferably in a range of 10,000 to 30,000. In a case where the weight-average molecular weight is equal to or lower than the upper limit of this range, the resist composition exhibits sufficiently satisfactory solubility in a solvent for a resist to be used as a resist composition. On the other hand, in a case where the weight-average molecular weight is equal to or greater than the lower limit of this range, water repellency of the resist film is excellent.

Further, the polydispersity (Mw/Mn) of the component (F) is preferably in a range of 1.0 to 5.0, more preferably in a range of 1.0 to 3.0, and most preferably in a range of 1.0 to 2.5.

In the resist composition according to the present embodiment, the component (F) may be used alone or in a combination of two or more kinds thereof.

In a case where the resist composition contains the component (F), the content of the component (F) is typically at a proportion of 0.5 to 10 parts by mass, with respect to 100 parts by mass of the component (A1).

<<Component (S)>>

The resist composition according to the present embodiment may be produced by dissolving the resist materials in an organic solvent (hereinafter, referred to as a “component (S)”).

The component (S) may be any organic solvent which can dissolve the respective components to be used to obtain a uniform solution, and optional organic solvent can be suitably selected from those which are conventionally known as solvents for a chemical amplification-type resist composition and then used.

Examples of the component (S) include lactones such as γ-butyrolactone; ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl-n-pentyl ketone, methyl isopentyl ketone, and 2-heptanone; polyhydric alcohols, such as ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol; compounds having an ester bond, such as ethylene glycol monoacetate, diethylene glycol monoacetate, propylene glycol monoacetate, and dipropylene glycol monoacetate; polyhydric alcohol derivatives including compounds having an ether bond, such as a monoalkyl ether (such as monomethyl ether, monoethyl ether, monopropyl ether or monobutyl ether) or monophenyl ether of any of these polyhydric alcohols or compounds having an ester bond (among these, propylene glycol monomethyl ether acetate (PGMEA) and propylene glycol monomethyl ether (PGME) are preferable); cyclic ethers such as dioxane; esters such as methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, and ethyl ethoxypropionate; aromatic organic solvents such as anisole, ethylbenzyl ether, cresylmethyl ether, diphenyl ether, dibenzyl ether, phenetole, butylphenyl ether, ethyl benzene, diethyl benzene, pentyl benzene, isopropyl benzene, toluene, xylene, cymene and mesitylene; and dimethylsulfoxide (DMSO).

In the resist composition according to the present embodiment, the component (S) may be used alone or as a mixed solvent of two or more kinds thereof. Among these, PGMEA, PGME, γ-butyrolactone, EL, and cyclohexanone are preferable.

Further, a mixed solvent obtained by mixing PGMEA with a polar solvent is also preferable as the component (S). The blending ratio (mass ratio) of the mixed solvent can be suitably determined, taking into consideration the compatibility of the PGMEA with the polar solvent, but is preferably in a range of 1:9 to 9:1 and more preferably in a range of 2:8 to 8:2.

More specifically, in a case where EL or cyclohexanone is blended as the polar solvent, the PGMEA:EL or cyclohexanone mass ratio is preferably in a range of 1:9 to 9:1 and more preferably in a range of 2:8 to 8:2. Alternatively, in a case where PGME is blended as the polar solvent, the PGMEA:PGME mass ratio is preferably in a range of 1:9 to 9:1, more preferably in a range of 2:8 to 8:2, and still more preferably in a range of 3:7 to 7:3. Furthermore, a mixed solvent of PGMEA, PGME, and cyclohexanone is also preferable.

Further, the component (S) is also preferably a mixed solvent of at least one selected from PGMEA and EL and γ-butyrolactone. In this case, as the mixing ratio, the mass ratio of the former to the latter is preferably in a range of 70:30 to 95:5.

The amount of the component (S) to be used is not particularly limited and is suitably set, depending on a thickness of a film to be coated, to a concentration at which the component (S) can be applied onto a substrate or the like. Generally, the component (S) is used such that the solid content concentration of the resist composition is in a range of 0.1% to 20% by mass and preferably in a range of 0.2% to 15% by mass.

As desired, other miscible additives can also be added to the resist composition according to the present embodiment. For example, for improving the performance of the resist film, an additive resin, a dissolution inhibitor, a plasticizer, a stabilizer, a colorant, a halation prevention agent, and a dye can be suitably contained therein.

After dissolving the resist material in the component (S), the resist composition according to the present embodiment may be subjected to removal of impurities and the like by using a porous polyimide film, a porous polyamideimide film, or the like. For example, the resist composition may be filtered using a filter made of a porous polyimide film, a filter made of a porous polyamideimide film, or a filter made of a porous polyimide film and a porous polyamideimide film. Examples of the porous polyimide film and the porous polyamideimide film include those described in Japanese Unexamined Patent Application, First Publication No. 2016-155121.

The resist composition according to the present embodiment described above contains the resin component (A1) having the constitutional unit (a01) and the constitutional unit (a02), and the acid generator component composed of the compound (B1) having an anion moiety and a cation moiety.

The constitutional unit (a01) is a constitutional unit having an unsaturated bond and two chain saturated hydrocarbon groups. The constitutional unit (a02) is a constitutional unit having a phenol skeleton (an aromatic ring having a hydroxy group). The compound (B1) is a compound (salt) in which an anion and a cation are ionically bonded. Due to the effect of the combination thereof, the compound (B1) can be more uniformly dispersed in the resist film.

As a result, the resist composition according to the present embodiment can form a resist pattern in which further high sensitivity is achieved and which is excellent in lithography characteristics and has high rectangularity.

(Method of Forming Resist Pattern)

The method of forming a resist pattern according to the second aspect of the present invention is a method including a step of forming a resist film on a support using the resist composition according to the first aspect described above, a step of exposing the resist film, and a step of developing the exposed resist film to form a resist pattern.

Examples of one embodiment of such a method of forming a resist pattern include a method of forming a resist pattern performed as described below.

First, the resist composition of the above-described embodiment is applied onto a support with a spinner or the like, and a baking (post-apply baking (PAB)) treatment is performed, for example, at a temperature condition of 80° C. to 150° C. for 40 to 120 seconds, preferably for 60 to 90 seconds to form a resist film.

Subsequently, the selective exposure is performed on the resist film, for example, by exposure through a mask (mask pattern) having a predetermined pattern formed on the mask by using a lithography apparatus such as an electron beam lithography apparatus or an EUV lithography apparatus, or by direct irradiation of the resist film for drawing with an electron beam without using a mask pattern. Thereafter, baking treatment (post-exposure baking (PEB)) is performed, for example, under a temperature condition in a range of 80° C. to 150° C. for 40 to 120 seconds and preferably 60 to 90 seconds.

Next, the resist film after the exposure and the PEB treatment is subjected to a developing treatment. The developing treatment is performed using an alkali developing solution in a case of an alkali developing process, and a developing solution containing an organic solvent (organic developing solution) in a case of a solvent developing process.

After the developing treatment, it is preferable to conduct a rinse treatment. As the rinse treatment, water rinsing using pure water is preferable in a case of an alkali developing process, and rinsing using a rinse liquid containing an organic solvent is preferable in a case of a solvent developing process.

In a case of a solvent developing process, after the developing treatment or the rinsing, the developing solution or the rinse liquid remaining on the pattern can be removed by a treatment using a supercritical fluid.

After the developing treatment or the rinse treatment, drying is conducted. As desired, baking treatment (post-baking) can be performed following the developing treatment.

In this manner, a resist pattern can be formed.

The support is not specifically limited and a conventionally known support can be used. For example, substrates for electronic components and such substrates having predetermined wiring patterns formed thereon can be used. Specific examples of the material of the substrate include metals such as silicon wafer, copper, chromium, iron and aluminum; and glass. As a material for the wiring pattern, copper, aluminum, nickel, gold, or the like can be used.

Further, as the support, any support having the above-described substrate on which an inorganic and/or organic film is provided may be used. Examples of the inorganic film include an inorganic antireflection film (inorganic BARC). Examples of the organic film include an organic antireflection film (organic BARC) and an organic film such as a lower-layer organic film used in a multilayer resist method.

Here, the multilayer resist method is a method in which at least one layer of an organic film (lower-layer organic film) and at least one layer of a resist film (upper-layer resist film) are provided on a substrate, and a resist pattern formed on the upper-layer resist film is used as a mask to conduct patterning of the lower-layer organic film.

This method is considered as being capable of forming a pattern with a high aspect ratio. More specifically, in the multilayer resist method, a desired thickness can be ensured by the lower-layer organic film, and as a result, the thickness of the resist film can be reduced, and a fine pattern with a high aspect ratio can be formed.

The multilayer resist method is classified into a method in which a double-layer structure consisting of an upper-layer resist film and a lower-layer organic film is formed (double-layer resist method), and a method in which a multilayer structure having at least three layers consisting of an upper-layer resist film, a lower-layer organic film and at least one intermediate layer (thin metal film or the like) provided between the upper-layer resist film and the lower-layer organic film (triple-layer resist method).

The wavelength to be used for exposure is not particularly limited and the exposure can be performed using radiation such as an ArF excimer laser, a KrF excimer laser, an F₂ excimer laser, extreme ultraviolet (EUV) rays, vacuum ultraviolet (VUV) rays, electron beams (EB), X-rays, or soft X-rays. The resist composition is highly useful for a KrF excimer laser, an ArF excimer laser, EB, or EUV, more useful for an ArF excimer laser, EB or EUV, and particularly useful for an ArF excimer laser. The method of forming a resist pattern according to the present embodiment is a particularly useful method in a case where the step of exposing the resist film includes an operation of exposing the resist film to extreme ultraviolet (EUV) rays or electron beams (EB).

The exposure of the resist film can be a general exposure (dry exposure) performed in air or an inert gas such as nitrogen, or liquid immersion exposure (liquid immersion lithography).

In liquid immersion lithography is an exposure method in which the region between the resist film and the lens at the lowermost position of the lithography apparatus is pre-filled with a solvent (liquid immersion medium) that has a larger refractive index than the refractive index of air, and the exposure (dipping exposure) is performed in this state.

The liquid immersion medium is preferably a solvent that exhibits a refractive index larger than a refractive index of air but smaller than a refractive index of the resist film to be exposed. The refractive index of the solvent is not particularly limited as long as it satisfies the above-described requirements.

Examples of the solvent which exhibits a refractive index that is larger than the refractive index of air but smaller than the refractive index of the resist film include water, fluorine-based inert liquids, silicone-based solvents, and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquids containing a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃, C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, and the boiling point is preferably in a range of 70 to 180° C. and more preferably in a range of 80° to 160° C. A fluorine-based inert liquid having a boiling point in the above-described range is advantageous in that removing the medium used in the liquid immersion after the exposure can be preferably performed by a simple method. The fluorine-based inert liquid is particularly preferably a perfluoroalkyl compound in which all of the hydrogen atoms of the alkyl group are substituted with a fluorine atom. Examples of these perfluoroalkyl compounds include perfluoroalkyl ether compounds and perfluoroalkyl amine compounds.

Specific examples of the perfluoroalkyl ether compound include perfluoro(2-butyl-tetrahydrofuran) (boiling point of 102° C.), and specific examples of the perfluoroalkyl amine compound include perfluorotributyl amine (boiling point of 174° C.).

As the liquid immersion medium, water is preferable in terms of cost, safety, environment, and versatility.

Examples of the alkali developing solution used for a developing treatment in an alkali developing process include a 0.1 to 10% by mass aqueous solution of tetramethylammonium hydroxide (TMAH).

As the organic solvent contained in the organic developing solution, which is used for a developing treatment in a solvent developing process, any one of the conventionally known organic solvents capable of dissolving the component (A) (component (A) prior to exposure) can be suitably selected from the conventionally known organic solvents. Specific examples of the organic solvent include polar solvents such as a ketone-based solvent, an ester-based solvent, an alcohol-based solvent, a nitrile-based solvent, an amide-based solvent, and an ether-based solvent, and hydrocarbon-based solvents.

A ketone-based solvent is an organic solvent containing C—C(═O)—C in the structure thereof. An ester-based solvent is an organic solvent containing C—C(═O)—O—C in the structure thereof. An alcohol-based solvent is an organic solvent containing an alcoholic hydroxy group in the structure thereof. An “alcoholic hydroxy group” indicates a hydroxy group bonded to a carbon atom of an aliphatic hydrocarbon group. A nitrile-based solvent is an organic solvent containing a nitrile group in the structure thereof. An amide-based solvent is an organic solvent containing an amide group in the structure thereof. An ether-based solvent is an organic solvent containing C—O—C in the structure thereof.

Some organic solvents have a plurality of the functional groups which characterize the above-described solvents in the structure thereof.

In such a case, the organic solvent can be classified as any type of solvent having a characteristic functional group. For example, diethylene glycol monomethyl ether can be classified as an alcohol-based solvent or an ether-based solvent.

A hydrocarbon-based solvent consists of a hydrocarbon which may be halogenated and does not have any substituent other than a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and, an iodine atom, and a fluorine atom is preferable.

Among the above, the organic solvent contained in the organic developing solution is preferably a polar solvent and more preferably a ketone-based solvent, an ester-based solvent, or a nitrile-based solvent.

Examples of ketone-based solvent include 1-octanone, 2-octanone, 1-nonanone, 2-nonanone, acetone, 4-heptanone, 1-hexanone, 2-hexanone, diisobutyl ketone, cyclohexanone, methylcyclohexanone, phenylacetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, acetonylacetone, ionone, diacetonyl alcohol, acetylcarbinol, acetophenone, methyl naphthyl ketone, isophorone, propylenecarbonate, γ-butyrolactone and methylamyl ketone (2-heptanone). Among these, the ketone-based solvent is preferably methylamyl ketone (2-heptanone).

Examples of the ester-based solvent include methyl acetate, butyl acetate, ethyl acetate, isopropyl acetate, amyl acetate, isoamyl acetate, ethyl methoxyacetate, ethyl ethoxyacetate, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monophenyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monopropyl ether acetate, diethylene glycol monophenyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, 2-methoxybutyl acetate, 3-methoxybutyl acetate, 4-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, 3-ethyl-3-methoxybutyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, 2-ethoxybutyl acetate, 4-ethoxybutyl acetate, 4-propoxybutyl acetate, 2-methoxypentyl acetate, 3-methoxypentyl acetate, 4-methoxypentyl acetate, 2-methyl-3-methoxypentyl acetate, 3-methyl-3-methoxypentyl acetate, 3-methyl-4-methoxypentyl acetate, 4-methyl-4-methoxypentyl acetate, propylene glycol diacetate, methyl formate, ethyl formate, butyl formate, propyl formate, ethyl lactate, butyl lactate, propyl lactate, ethyl carbonate, propyl carbonate, butyl carbonate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, butyl pyruvate, methyl acetoacetate, ethyl acetoacetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate, methyl-3-methoxypropionate, ethyl-3-methoxypropionate, ethyl-3-ethoxypropionate, and propyl-3-methoxypropionate. Among these, the ester-based solvent is preferably butyl acetate.

Examples of the nitrile-based solvent include acetonitrile, propionitrile, valeronitrile, and butyronitrile.

As desired, the organic developing solution may have a conventionally known additive blended. Examples of the additive include surfactants. The surfactant is not particularly limited, and for example, an ionic or non-ionic fluorine-based and/or a silicone-based surfactant can be used. The surfactant is preferably a non-ionic surfactant and more preferably a non-ionic fluorine surfactant or a non-ionic silicone-based surfactant.

In a case where a surfactant is blended, the amount of the surfactant to be blended is typically in a range of 0.001% to 5% by mass, preferably in a range of 0.005% to 2% by mass, and more preferably in a range of 0.01% to 0.5% by mass with respect to the total amount of the organic developing solution.

The method of forming a resist pattern according to the present embodiment is a useful method in a case where the development is performed using an alkali developing solution.

The developing treatment can be performed by a conventionally known developing method. Examples thereof include a method in which the support is immersed in the developing solution for a predetermined time (a dip method), a method in which the developing solution is cast upon the surface of the support by surface tension and maintained for a predetermined period (a puddle method), a method in which the developing solution is sprayed onto the surface of the support (spray method), and a method in which a developing solution is continuously ejected from a developing solution-ejecting nozzle and applied to a support which is scanned at a constant rate while being rotated at a constant rate (dynamic dispense method).

As the organic solvent contained in the rinse liquid used in the rinse treatment after the developing treatment in a case of a solvent developing process, an organic solvent hardly dissolving the resist pattern can be suitably selected and used, among the organic solvents mentioned as organic solvents that are used for the organic developing solution. In general, at least one kind of solvent selected from the group consisting of a hydrocarbon-based solvent, a ketone-based solvent, an ester-based solvent, an alcohol-based solvent, an amide-based solvent, and an ether-based solvent is used. Among these, at least one kind of solvent selected from the group consisting of a hydrocarbon-based solvent, a ketone-based solvent, an ester-based solvent, an alcohol-based solvent, and an amide-based solvent is preferable, at least one kind of solvent selected from the group consisting of an alcohol-based solvent and an ester-based solvent is more preferable, and an alcohol-based solvent is particularly preferable.

The alcohol-based solvent used for the rinse liquid is preferably a monohydric alcohol of 6 to 8 carbon atoms, and the monohydric alcohol may be linear, branched, or cyclic. Specific examples thereof include 1-hexanol, 1-heptanol, 1-octanol, 2-hexanol, 2-heptanol, 2-octanol, 3-hexanol, 3-heptanol, 3-octanol, 4-octanol, and benzyl alcohol. Among these, 1-hexanol, 2-heptanol, and 2-hexanol are preferable, and 1-hexanol and 2-hexanol are more preferable.

As the organic solvent, one kind of solvent may be used alone, or two or more kinds of solvents may be used in combination. Further, an organic solvent other than the above-described examples or water may be mixed thereto. However, in consideration of the development characteristics, the amount of water to be blended in the rinse liquid is preferably 30% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less, and most preferably 3% by mass or less with respect to the total amount of the rinse liquid.

A conventionally known additive can be blended with the rinse liquid as necessary. Examples of the additive include surfactants. Examples of the surfactant include the same surfactants as those described above, the surfactant is preferably a non-ionic surfactant and more preferably a non-ionic fluorine surfactant or a non-ionic silicone-based surfactant.

In a case where a surfactant is blended, the amount of the surfactant to be blended is typically in a range of 0.001% to 5% by mass, preferably in a range of 0.005% to 2% by mass, and more preferably in a range of 0.01% to 0.5% by mass with respect to the total amount of the rinse liquid.

The rinse treatment using a rinse liquid (washing treatment) can be performed by a conventionally known rinse method. Examples of the rinse treatment method include a method in which the rinse liquid is continuously applied to the support while rotating it at a constant rate (rotational coating method), a method in which the support is immersed in the rinse liquid for a predetermined time (dip method), and a method in which the rinse liquid is sprayed onto the surface of the support (spray method).

According to the method of forming a resist pattern according to the present embodiment described above, since the resist composition according to the present embodiment described above is used, it is possible to form a resist pattern which is highly sensitive, is excellent in lithography characteristics, and has high rectangularity.

EXAMPLES

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to these Examples.

Preparation of resist composition Examples 1 to 13 and Comparative Examples 1 to 6

Each of the components shown in Tables 1 and 2 was mixed and dissolved to prepare a resist composition of each Example.

TABLE 1 Component Component Component Component (A) (B) (D) (S) Example 1 (A1)-1 (B1)-1 (D)-1 (S)-1 [100] [21.3] [3.8] [6,600] Example 2 (A1)-2 (B1)-1 (D)-1 (S)-1 [100] [21.3] [3.8] [6,600] Example 3 (A1)-2 (B1)-2 (D)-1 (S)-1 [100] [29.8] [3.8] [6,600] Example 4 (A1)-2 (B1)-3 (D)-1 (S)-1 [100] [22.4] [3.8] [6,600] Example 5 (A1)-3 (B1)-1 (D)-1 (S)-1 [100] [21.3] [3.8] [6,600] Example 6 (A1)-3 (B1)-4 (D)-1 (S)-1 [100] [24.7] [3.8] [6,600] Example 7 (A1)-4 (B1)-1 (D)-1 (S)-1 [100] [21.3] [3.8] [6,600] Example 8 (A1)-4 (B1)-5 (D)-1 (S)-1 [100] [22.3] [3.8] [6,600] Example 9 (A1)-5 (B1)-1 (D)-1 (S)-1 [100] [21.3] [3.8] [6,600] Example 10 (A1)-5 (B1)-6 (D)-1 (S)-1 [100] [14.3] [3.8] [6,600] Example 11 (A1)-6 (B1)-1 (D)-1 (S)-1 [100] [21.3] [3.8] [6,600] Example 12 (A1)-6 (B1)-7 (D)-1 (S)-1 [100] [25.3] [3.8] [6,600] Example 13 (A1)-3 (B1)-1 (D)-2 (S)-1 [100] [21.3] [3.0] [6,600]

TABLE 2 Component Component Component Component (A) (B) (D) (S) Comparative (A2)-1 (B1)-1 (D)-1 (S)-1 Example 1 [100] [21.3] [3.8] [6,600] Comparative (A2)-2 (B1)-1 (D)-1 (S)-1 Example 2 [100] [21.3] [3.8] [6,600] Comparative (A2)-3 (B1)-1 (D)-1 (S)-1 Example 3 [100] [21.3] [3.8] [6,600] Comparative (A2)-4 (B1)-1 (D)-1 (S)-1 Example 4 [100] [21.3] [3.8] [6,600] Comparative (A1)-3 (B2)-1 — (S)-1 Example 5 [100] [13.2] [6,600] Comparative (A1)-3 (B2)-1 (D)-2 (S)-1 Example 6 [100] [13.2] [3.0] [6,600]

In Tables 1 and 2, each abbreviation has the following meaning. The numerical values in the brackets are blending amounts (parts by mass).

(A1)-1: a high-molecular-weight compound represented by Chemical Formula (A1-1). The standard polystyrene-equivalent weight-average molecular weight (Mw) determined by GPC measurement and the molecular weight polydispersity (Mw/Mn) are respectively 6,900 and 1.78. The copolymerization compositional ratio (the ratio (molar ratio) among constitutional units in the structural formula) determined by ¹³C-NMR is l/m=50/50.

(A1)-2: a high-molecular-weight compound represented by Chemical Formula (A1-2). The standard polystyrene-equivalent weight-average molecular weight (Mw) determined by GPC measurement and the molecular weight polydispersity (Mw/Mn) are respectively 6,700 and 1.80. The copolymerization compositional ratio (the ratio (molar ratio) among constitutional units in the structural formula) determined by ¹³C-NMR is l/m=50/50.

(A1)-3: a high-molecular-weight compound represented by Chemical Formula (A1-3). The standard polystyrene-equivalent weight-average molecular weight (Mw) determined by GPC measurement and the molecular weight polydispersity (Mw/Mn) are respectively 6,700 and 1.76. The copolymerization compositional ratio (the ratio (molar ratio) among constitutional units in the structural formula) determined by ¹³C-NMR is l/m=50/50.

(A1)-4: a high-molecular-weight compound represented by Chemical Formula (A1-4). The standard polystyrene-equivalent weight-average molecular weight (Mw) determined by GPC measurement and the molecular weight polydispersity (Mw/Mn) are respectively 6,600 and 1.66. The copolymerization compositional ratio (the ratio (molar ratio) among constitutional units in the structural formula) determined by ¹³C-NMR is l/m=50/50.

(A1)-5: a high-molecular-weight compound represented by Chemical Formula (A1-5). The standard polystyrene-equivalent weight-average molecular weight (Mw) determined by GPC measurement and the molecular weight polydispersity (Mw/Mn) are respectively 6,700 and 1.82. The copolymerization compositional ratio (the ratio (molar ratio) among constitutional units in the structural formula) determined by ¹³C-NMR is l/m=50/50.

(A1)-6: a high-molecular-weight compound represented by Chemical Formula (A1-6). The standard polystyrene-equivalent weight-average molecular weight (Mw) determined by GPC measurement and the molecular weight polydispersity (Mw/Mn) are respectively 7,000 and 1.72. The copolymerization compositional ratio (the ratio (molar ratio) among constitutional units in the structural formula) determined by ¹³C-NMR is l/m=50/50.

(A2)-1: a high-molecular-weight compound represented by Chemical Formula (A2-1). The standard polystyrene-equivalent weight-average molecular weight (Mw) determined by GPC measurement and the molecular weight polydispersity (Mw/Mn) are respectively 6,400 and 1.77. The copolymerization compositional ratio (the ratio (molar ratio) among constitutional units in the structural formula) determined by ¹³C-NMR is l/m=50/50.

(A2)-2: a high-molecular-weight compound represented by Chemical Formula (A2-2). The standard polystyrene-equivalent weight-average molecular weight (Mw) determined by GPC measurement and the molecular weight polydispersity (Mw/Mn) are respectively 6,700 and 1.83. The copolymerization compositional ratio (the ratio (molar ratio) among constitutional units in the structural formula) determined by ¹³C-NMR is l/m=50/50.

(A2)-3: a high-molecular-weight compound represented by Chemical Formula (A2-3). The standard polystyrene-equivalent weight-average molecular weight (Mw) determined by GPC measurement and the molecular weight polydispersity (Mw/Mn) are respectively 6,800 and 1.81. The copolymerization compositional ratio (the ratio (molar ratio) among constitutional units in the structural formula) determined by ¹³C-NMR is l/m=50/50.

(A2)-4: a high-molecular-weight compound represented by Chemical Formula (A2-4). The standard polystyrene-equivalent weight-average molecular weight (Mw) determined by GPC measurement and the molecular weight polydispersity (Mw/Mn) are respectively 6,500 and 1.72. The copolymerization compositional ratio (the ratio (molar ratio) among constitutional units in the structural formula) determined by ¹³C-NMR is l/m=50/50.

(B1)-1 to (B1)-7: acid generators composed of compounds respectively represented by Chemical Formulae (B1-1) to (B1-7) described below.

(B2)-1: an acid generator composed of a compound represented by Chemical Formula (B2-1).

(D)-1: an acid diffusion-controlling agent composed of a compound represented by Chemical Formula (D-1).

(D)-2: an acid diffusion-controlling agent composed of a compound represented by Chemical Formula (D-2).

(S)-1: a mixed solvent of propylene glycol monomethyl ether acetate/propylene glycol monomethyl ether=80/20 (mass ratio)

<Formation of Resist Pattern>

Next, the resist composition of each Example was applied onto an 8-inch silicon substrate which had been subjected to a hexamethyldisilazane (HMDS) treatment using a spinner, the coated wafer was subjected to a post-apply baking (PAB) treatment on a hot plate at a temperature of 110° C. for 60 seconds so that the coated wafer was dried to form a resist film having a film thickness of 50 nm.

Next, drawing (exposure) was performed on the resist film by using an electron beam lithography apparatus JEOL-JBX-9300FS (manufactured by JEOL Ltd.), with the target size being set to a 1:1 line-and-space pattern (hereinafter, described as an “LS pattern”) of a line width of 50 nm, at an accelerating voltage of 100 kV.

Thereafter, a post-exposure baking (PEB) treatment was performed on the resist film at 110° C. for 60 seconds.

Subsequently, alkali development was performed at 23° C. for 60 seconds using a 2.38% by mass tetramethylammonium hydroxide (TMAH) aqueous solution “NMD-3” (trade name, manufactured by TOKYO OHKA KOGYO CO., LTD.).

Thereafter, rinsing was performed with pure water for 15 seconds.

As a result, a 1:1 LS pattern having a line width of 50 nm was formed.

[Evaluation of Optimum Exposure Amount (Eop)]

According to <Formation of resist pattern> described above, an optimum exposure amount Eop (μC/cm²) for forming the LS pattern having the target size (line width of 50 nm) was determined. The results are shown in Table 3 as “Eop (μC/cm²)”.

[Evaluation of Linewise Roughness (LWR)]

36 of the LS pattern having the target size (a line width of 50 nm) formed in <Formation of resist pattern> described above, which is a scale indicating LWR, was determined. The results are shown in Table 3 as “LWR (nm)”.

“3σ” indicates a triple value (unit: nm) of the standard deviation (a) determined from measurement results obtained by measuring 400 line positions in the longitudinal direction of the line with a scanning electron microscope (accelerating voltage: 800V, trade name: S-9380, manufactured by Hitachi High-Tech Corporation) The smaller the value of 3a is, the smaller the roughness in the line side wall is, which means an LS pattern having a more uniform width was obtained.

[Evaluation of LS Pattern Shape]

The cross-sectional shape of the obtained LS pattern having the target size (line width of 50 nm), which was formed in <Formation of resist pattern> described above, was observed using a scanning electron microscope (accelerating voltage: 300V, trade name: SU8000, manufactured by Hitachi High-Tech Corporation). The shape was evaluated according to the following evaluation criteria. The results are shown in Table 3 as “Pattern shape”.

A: The cross-sectional shape of the pattern was rectangular.

B: The cross-sectional shape of the pattern was not rectangular.

TABLE 3 PAB PEB Eop LWR Pattern (° C.) (° C.) (μC/cm²) (nm) shape Example 1 110 110 115 5.1 A Example 2 110 110 115 5.2 A Example 3 110 110 120 5.1 A Example 4 110 110 115 5.3 A Example 5 110 110 100 5.2 A Example 6 110 110 105 5.3 A Example 7 110 110 110 5.2 A Example 8 110 110 100 5.4 A Example 9 110 110 110 4.8 A Example 10 110 110 110 5.1 A Example 11 110 110 115 5.0 A Example 12 110 110 110 5.3 A Example 13 110 110 115 5.6 A Comparative 110 110 120 6.8 B Example 1 Comparative 110 110 120 5.8 B Example 2 Comparative 110 110 130 6.5 B Example 3 Comparative 110 110 120 6.5 B Example 4 Comparative 110 110 105 7.4 B Example 5 Comparative 110 110 135 8.2 B Example 6

From the results shown in Table 3, it can be confirmed that the resist compositions of Examples 1 to 13, to which the present invention was applied, can form a resist pattern that is excellent in all of the sensitivity, the roughness reduction property, and the rectangularity of the pattern in the formation of the resist pattern.

While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the invention. Accordingly, the invention is not to be considered as being limited by the foregoing description and is only limited by the scope of the appended claims. 

What is claimed is:
 1. A resist composition generating an acid upon exposure and having solubility in a developing solution, which is changed by action of an acid, the resist composition comprising: a resin component (A1) having solubility in a developing solution, which is changed by action of an acid; and an acid generator component (B) generating an acid upon exposure, wherein the resin component (A1) has a constitutional unit (a01) derived from a compound represented by General Formula (a01-1) and a constitutional unit (a02) derived from a compound represented by General Formula (a02-1), and the acid generator component (B) is a compound (B1) having an anion moiety and a cation moiety:

wherein, in General Formula (a01-1), W¹ represents a polymerizable group-containing group, C^(t) represents a tertiary carbon atom, R¹¹ represents an unsaturated hydrocarbon group which may have a substituent, R¹² and R¹³ each independently represent a chain saturated hydrocarbon group which may have a substituent, provided that a carbon atom at an α-position of C^(t) constitutes a carbon-carbon unsaturated bond; in General Formula (a02-1), W² represents a polymerizable group-containing group, Wa² represents an aromatic hydrocarbon group, part or all of hydrogen atoms which the aromatic hydrocarbon group has may be substituted with a substituent other than a hydroxy group, W² and Wa² may form a condensed ring, and n2 represents an integer in a range of 1 to
 3. 2. The resist composition according to claim 1, wherein the constitutional unit (a01) is a constitutional unit represented by General Formula (a01-1-1):

wherein R⁰¹ represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms, C^(t) represents a tertiary carbon atom, Ra⁰⁰¹ to Ra⁰⁰³ each independently represents a hydrogen atom, a monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms, or a monovalent cyclic hydrocarbon group having 3 to 20 carbon atoms, part or all of hydrogen atoms which the chain saturated hydrocarbon group and the cyclic hydrocarbon group have may be substituted with a substituent, and R¹² and R¹³ each independently represent a chain saturated hydrocarbon group which may have a substituent.
 3. The resist composition according to claim 1, wherein the constitutional unit (a02) is a constitutional unit represented by General Formula (a02-1-1) or a constitutional unit represented by General Formula (a02-1-2):

wherein, in General Formula (a02-1-1), R⁰²¹ represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms, Wa²¹ represents an aromatic hydrocarbon group, part or all of hydrogen atoms which the aromatic hydrocarbon group has may be substituted with a substituent other than a hydroxy group, and n21 represents an integer in a range of 1 to 3; in General Formula (a02-1-2), R⁰²² represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms, Wa²² represents an aromatic hydrocarbon group, part or all of hydrogen atoms which the aromatic hydrocarbon group has may be substituted with a substituent other than a hydroxy group, and n22 represents an integer in a range of 1 to
 3. 4. A method of forming a resist pattern, comprising: forming a resist film on a support using the resist composition according to claim 1; exposing the resist film; and developing the exposed resist film to form a resist pattern.
 5. The method of forming a resist pattern according to claim 4, wherein the resist film is exposed to extreme ultraviolet (EUV) rays or electron beams (EB). 